@@ -90,13 +90,11 @@ class SampledPlot:
             fraction = min(1., fraction)
         self.fraction = fraction
 
-        if isinstance(data, DataFrame):
+        if isinstance(data, (DataFrame, Series)):
+            if isinstance(data, Series):
+                data = data.to_frame()
             sampled = data._sdf.sample(fraction=self.fraction)
             return DataFrame(data._internal.copy(sdf=sampled)).to_pandas()
-        elif isinstance(data, Series):
-            scol = data._scol
-            sampled = data._kdf._sdf.sample(fraction=self.fraction)
-            return DataFrame(data._kdf._internal.copy(sdf=sampled, scol=scol)).to_pandas()
         else:
             ValueError("Only DataFrame and Series are supported for plotting.")
 
#
# Copyright (C) 2019 Databricks, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from distutils.version import LooseVersion

import matplotlib
import numpy as np
import pandas as pd
from matplotlib.axes._base import _process_plot_format
from pandas.core.dtypes.inference import is_integer, is_list_like
from pandas.io.formats.printing import pprint_thing
from pandas.core.base import PandasObject
from pyspark.ml.feature import Bucketizer
from pyspark.sql import functions as F

from databricks.koalas.missing import _unsupported_function
from databricks.koalas.config import get_option


def _gca(rc=None):
    import matplotlib.pyplot as plt
    with plt.rc_context(rc):
        return plt.gca()


def _get_standard_kind(kind):
    return {'density': 'kde'}.get(kind, kind)


if LooseVersion(pd.__version__) < LooseVersion('0.25'):
    from pandas.plotting._core import _all_kinds, BarPlot, BoxPlot, HistPlot, MPLPlot, PiePlot, \
        AreaPlot, LinePlot, BarhPlot, ScatterPlot
else:
    from pandas.plotting._core import PlotAccessor
    from pandas.plotting._matplotlib import BarPlot, BoxPlot, HistPlot, PiePlot, AreaPlot, \
        LinePlot, BarhPlot, ScatterPlot
    from pandas.plotting._matplotlib.core import MPLPlot
    _all_kinds = PlotAccessor._all_kinds


class TopNPlot:

    def get_top_n(self, data):
        from databricks.koalas import DataFrame, Series
        max_rows = get_option("plotting.max_rows")
        # Simply use the first 1k elements and make it into a pandas dataframe
        # For categorical variables, it is likely called from df.x.value_counts().plot.xxx().
        if isinstance(data, Series):
            data = data.head(max_rows + 1).to_pandas().to_frame()
        elif isinstance(data, DataFrame):
            data = data.head(max_rows + 1).to_pandas()
        else:
            ValueError("Only DataFrame and Series are supported for plotting.")

        self.partial = False
        if len(data) > max_rows:
            self.partial = True
            data = data.iloc[:max_rows]
        return data

    def set_result_text(self, ax):
        max_rows = get_option("plotting.max_rows")
        assert hasattr(self, "partial")

        if self.partial:
            ax.text(1, 1, 'showing top {} elements only'.format(max_rows),
                    size=6, ha='right', va='bottom',
                    transform=ax.transAxes)


class SampledPlot:
    def get_sampled(self, data):
        from databricks.koalas import DataFrame, Series
        fraction = get_option("plotting.sample_ratio")
        if fraction is None:
            fraction = 1 / (len(data) / get_option("plotting.max_rows"))
            fraction = min(1., fraction)
        self.fraction = fraction

        if isinstance(data, DataFrame):
            sampled = data._sdf.sample(fraction=self.fraction)
            return DataFrame(data._internal.copy(sdf=sampled)).to_pandas()
        elif isinstance(data, Series):
            scol = data._scol
            sampled = data._kdf._sdf.sample(fraction=self.fraction)
            return DataFrame(data._kdf._internal.copy(sdf=sampled, scol=scol)).to_pandas()
        else:
            ValueError("Only DataFrame and Series are supported for plotting.")

    def set_result_text(self, ax):
        assert hasattr(self, "fraction")

        if self.fraction < 1:
            ax.text(
                1, 1, 'showing the sampled result by fraction %s' % self.fraction,
                size=6, ha='right', va='bottom',
                transform=ax.transAxes)


class KoalasBarPlot(BarPlot, TopNPlot):
    def __init__(self, data, **kwargs):
        super(KoalasBarPlot, self).__init__(self.get_top_n(data), **kwargs)

    def _plot(self, ax, x, y, w, start=0, log=False, **kwds):
        self.set_result_text(ax)
        return ax.bar(x, y, w, bottom=start, log=log, **kwds)


class KoalasBoxPlotSummary:
    def __init__(self, data, colname):
        self.data = data
        self.colname = colname

    def compute_stats(self, whis, precision):
        # Computes mean, median, Q1 and Q3 with approx_percentile and precision
        pdf = (self.data._kdf._sdf
               .agg(*[F.expr('approx_percentile({}, {}, {})'.format(self.colname, q,
                                                                    1. / precision))
                      .alias('{}_{}%'.format(self.colname, int(q * 100)))
                      for q in [.25, .50, .75]],
                    F.mean(self.colname).alias('{}_mean'.format(self.colname))).toPandas())

        # Computes IQR and Tukey's fences
        iqr = '{}_iqr'.format(self.colname)
        p75 = '{}_75%'.format(self.colname)
        p25 = '{}_25%'.format(self.colname)
        pdf.loc[:, iqr] = pdf.loc[:, p75] - pdf.loc[:, p25]
        pdf.loc[:, '{}_lfence'.format(self.colname)] = pdf.loc[:, p25] - whis * pdf.loc[:, iqr]
        pdf.loc[:, '{}_ufence'.format(self.colname)] = pdf.loc[:, p75] + whis * pdf.loc[:, iqr]

        qnames = ['25%', '50%', '75%', 'mean', 'lfence', 'ufence']
        col_summ = pdf[['{}_{}'.format(self.colname, q) for q in qnames]]
        col_summ.columns = qnames
        lfence, ufence = col_summ['lfence'], col_summ['ufence']

        stats = {'mean': col_summ['mean'].values[0],
                 'med': col_summ['50%'].values[0],
                 'q1': col_summ['25%'].values[0],
                 'q3': col_summ['75%'].values[0]}

        return stats, (lfence.values[0], ufence.values[0])

    def outliers(self, lfence, ufence):
        # Builds expression to identify outliers
        expression = F.col(self.colname).between(lfence, ufence)
        # Creates a column to flag rows as outliers or not
        return self.data._kdf._sdf.withColumn('__{}_outlier'.format(self.colname), ~expression)

    def calc_whiskers(self, outliers):
        # Computes min and max values of non-outliers - the whiskers
        minmax = (outliers
                  .filter('not __{}_outlier'.format(self.colname))
                  .agg(F.min(self.colname).alias('min'),
                       F.max(self.colname).alias('max'))
                  .toPandas())
        return minmax.iloc[0][['min', 'max']].values

    def get_fliers(self, outliers):
        # Filters only the outliers, should "showfliers" be True
        fliers_df = outliers.filter('__{}_outlier'.format(self.colname))

        # If shows fliers, takes the top 1k with highest absolute values
        fliers = (fliers_df
                  .select(F.abs(F.col('`{}`'.format(self.colname))).alias(self.colname))
                  .orderBy(F.desc('`{}`'.format(self.colname)))
                  .limit(1001)
                  .toPandas()[self.colname].values)

        return fliers


class KoalasBoxPlot(BoxPlot):
    @staticmethod
    def rc_defaults(notch=None, vert=None, whis=None,
                    patch_artist=None, bootstrap=None, meanline=None,
                    showmeans=None, showcaps=None, showbox=None,
                    showfliers=None, **kwargs):
        # Missing arguments default to rcParams.
        if whis is None:
            whis = matplotlib.rcParams['boxplot.whiskers']
        if bootstrap is None:
            bootstrap = matplotlib.rcParams['boxplot.bootstrap']

        if notch is None:
            notch = matplotlib.rcParams['boxplot.notch']
        if vert is None:
            vert = matplotlib.rcParams['boxplot.vertical']
        if patch_artist is None:
            patch_artist = matplotlib.rcParams['boxplot.patchartist']
        if meanline is None:
            meanline = matplotlib.rcParams['boxplot.meanline']
        if showmeans is None:
            showmeans = matplotlib.rcParams['boxplot.showmeans']
        if showcaps is None:
            showcaps = matplotlib.rcParams['boxplot.showcaps']
        if showbox is None:
            showbox = matplotlib.rcParams['boxplot.showbox']
        if showfliers is None:
            showfliers = matplotlib.rcParams['boxplot.showfliers']

        return dict(whis=whis, bootstrap=bootstrap, notch=notch, vert=vert,
                    patch_artist=patch_artist, meanline=meanline, showmeans=showmeans,
                    showcaps=showcaps, showbox=showbox, showfliers=showfliers)

    def boxplot(self, ax, bxpstats, notch=None, sym=None, vert=None,
                whis=None, positions=None, widths=None, patch_artist=None,
                bootstrap=None, usermedians=None, conf_intervals=None,
                meanline=None, showmeans=None, showcaps=None,
                showbox=None, showfliers=None, boxprops=None,
                labels=None, flierprops=None, medianprops=None,
                meanprops=None, capprops=None, whiskerprops=None,
                manage_xticks=True, autorange=False, zorder=None,
                precision=None):

        def _update_dict(dictionary, rc_name, properties):
            """ Loads properties in the dictionary from rc file if not already
            in the dictionary"""
            rc_str = 'boxplot.{0}.{1}'
            if dictionary is None:
                dictionary = dict()
            for prop_dict in properties:
                dictionary.setdefault(prop_dict,
                                      matplotlib.rcParams[rc_str.format(rc_name, prop_dict)])
            return dictionary

        # Common property dictionnaries loading from rc
        flier_props = ['color', 'marker', 'markerfacecolor', 'markeredgecolor',
                       'markersize', 'linestyle', 'linewidth']
        default_props = ['color', 'linewidth', 'linestyle']

        boxprops = _update_dict(boxprops, 'boxprops', default_props)
        whiskerprops = _update_dict(whiskerprops, 'whiskerprops',
                                    default_props)
        capprops = _update_dict(capprops, 'capprops', default_props)
        medianprops = _update_dict(medianprops, 'medianprops', default_props)
        meanprops = _update_dict(meanprops, 'meanprops', default_props)
        flierprops = _update_dict(flierprops, 'flierprops', flier_props)

        if patch_artist:
            boxprops['linestyle'] = 'solid'
            boxprops['edgecolor'] = boxprops.pop('color')

        # if non-default sym value, put it into the flier dictionary
        # the logic for providing the default symbol ('b+') now lives
        # in bxp in the initial value of final_flierprops
        # handle all of the `sym` related logic here so we only have to pass
        # on the flierprops dict.
        if sym is not None:
            # no-flier case, which should really be done with
            # 'showfliers=False' but none-the-less deal with it to keep back
            # compatibility
            if sym == '':
                # blow away existing dict and make one for invisible markers
                flierprops = dict(linestyle='none', marker='', color='none')
                # turn the fliers off just to be safe
                showfliers = False
            # now process the symbol string
            else:
                # process the symbol string
                # discarded linestyle
                _, marker, color = _process_plot_format(sym)
                # if we have a marker, use it
                if marker is not None:
                    flierprops['marker'] = marker
                # if we have a color, use it
                if color is not None:
                    # assume that if color is passed in the user want
                    # filled symbol, if the users want more control use
                    # flierprops
                    flierprops['color'] = color
                    flierprops['markerfacecolor'] = color
                    flierprops['markeredgecolor'] = color

        # replace medians if necessary:
        if usermedians is not None:
            if (len(np.ravel(usermedians)) != len(bxpstats) or
                    np.shape(usermedians)[0] != len(bxpstats)):
                raise ValueError('usermedians length not compatible with x')
            else:
                # reassign medians as necessary
                for stats, med in zip(bxpstats, usermedians):
                    if med is not None:
                        stats['med'] = med

        if conf_intervals is not None:
            if np.shape(conf_intervals)[0] != len(bxpstats):
                err_mess = 'conf_intervals length not compatible with x'
                raise ValueError(err_mess)
            else:
                for stats, ci in zip(bxpstats, conf_intervals):
                    if ci is not None:
                        if len(ci) != 2:
                            raise ValueError('each confidence interval must '
                                             'have two values')
                        else:
                            if ci[0] is not None:
                                stats['cilo'] = ci[0]
                            if ci[1] is not None:
                                stats['cihi'] = ci[1]

        artists = ax.bxp(bxpstats, positions=positions, widths=widths,
                         vert=vert, patch_artist=patch_artist,
                         shownotches=notch, showmeans=showmeans,
                         showcaps=showcaps, showbox=showbox,
                         boxprops=boxprops, flierprops=flierprops,
                         medianprops=medianprops, meanprops=meanprops,
                         meanline=meanline, showfliers=showfliers,
                         capprops=capprops, whiskerprops=whiskerprops,
                         manage_xticks=manage_xticks, zorder=zorder)
        return artists

    def _plot(self, ax, bxpstats, column_num=None, return_type='axes', **kwds):
        bp = self.boxplot(ax, bxpstats, **kwds)

        if return_type == 'dict':
            return bp, bp
        elif return_type == 'both':
            return self.BP(ax=ax, lines=bp), bp
        else:
            return ax, bp

    def _compute_plot_data(self):
        colname = self.data.name
        summary = KoalasBoxPlotSummary(self.data, colname)

        # Updates all props with the rc defaults from matplotlib
        self.kwds.update(KoalasBoxPlot.rc_defaults(**self.kwds))

        # Gets some important kwds
        showfliers = self.kwds.get('showfliers', False)
        whis = self.kwds.get('whis', 1.5)
        labels = self.kwds.get('labels', [colname])

        # This one is Koalas specific to control precision for approx_percentile
        precision = self.kwds.get('precision', 0.01)

        # # Computes mean, median, Q1 and Q3 with approx_percentile and precision
        col_stats, col_fences = summary.compute_stats(whis, precision)

        # # Creates a column to flag rows as outliers or not
        outliers = summary.outliers(*col_fences)

        # # Computes min and max values of non-outliers - the whiskers
        whiskers = summary.calc_whiskers(outliers)

        if showfliers:
            fliers = summary.get_fliers(outliers)
        else:
            fliers = []

        # Builds bxpstats dict
        stats = []
        item = {'mean': col_stats['mean'],
                'med': col_stats['med'],
                'q1': col_stats['q1'],
                'q3': col_stats['q3'],
                'whislo': whiskers[0],
                'whishi': whiskers[1],
                'fliers': fliers,
                'label': labels[0]}
        stats.append(item)

        self.data = {labels[0]: stats}

    def _make_plot(self):
        bxpstats = list(self.data.values())[0]
        ax = self._get_ax(0)
        kwds = self.kwds.copy()

        for stats in bxpstats:
            if len(stats['fliers']) > 1000:
                stats['fliers'] = stats['fliers'][:1000]
                ax.text(1, 1, 'showing top 1,000 fliers only', size=6, ha='right', va='bottom',
                        transform=ax.transAxes)

        ret, bp = self._plot(ax, bxpstats, column_num=0,
                             return_type=self.return_type, **kwds)
        self.maybe_color_bp(bp)
        self._return_obj = ret

        labels = [l for l, _ in self.data.items()]
        labels = [pprint_thing(l) for l in labels]
        if not self.use_index:
            labels = [pprint_thing(key) for key in range(len(labels))]
        self._set_ticklabels(ax, labels)


class KoalasHistPlotSummary:
    def __init__(self, data, colname):
        self.data = data
        self.colname = colname

    def get_bins(self, n_bins):
        boundaries = (self.data._kdf._sdf
                      .agg(F.min(self.colname),
                           F.max(self.colname))
                      .rdd
                      .map(tuple)
                      .collect()[0])
        # divides the boundaries into bins
        return np.linspace(boundaries[0], boundaries[1], n_bins + 1)

    def calc_histogram(self, bins):
        bucket_name = '__{}_bucket'.format(self.colname)
        # creates a Bucketizer to get corresponding bin of each value
        bucketizer = Bucketizer(splits=bins,
                                inputCol=self.colname,
                                outputCol=bucket_name,
                                handleInvalid="skip")
        # after bucketing values, groups and counts them
        result = (bucketizer
                  .transform(self.data._kdf._sdf)
                  .select(bucket_name)
                  .groupby(bucket_name)
                  .agg(F.count('*').alias('count'))
                  .toPandas()
                  .sort_values(by=bucket_name))

        # generates a pandas DF with one row for each bin
        # we need this as some of the bins may be empty
        indexes = pd.DataFrame({bucket_name: np.arange(0, len(bins) - 1),
                                'bucket': bins[:-1]})
        # merges the bins with counts on it and fills remaining ones with zeros
        data = indexes.merge(result, how='left', on=[bucket_name]).fillna(0)[['count']]
        data.columns = [bucket_name]

        return data


class KoalasHistPlot(HistPlot):
    def _args_adjust(self):
        if is_integer(self.bins):
            summary = KoalasHistPlotSummary(self.data, self.data.name)
            # computes boundaries for the column
            self.bins = summary.get_bins(self.bins)

        if is_list_like(self.bottom):
            self.bottom = np.array(self.bottom)

    @classmethod
    def _plot(cls, ax, y, style=None, bins=None, bottom=0, column_num=0,
              stacking_id=None, **kwds):
        if column_num == 0:
            cls._initialize_stacker(ax, stacking_id, len(bins) - 1)

        base = np.zeros(len(bins) - 1)
        bottom = bottom + \
            cls._get_stacked_values(ax, stacking_id, base, kwds['label'])

        # Since the counts were computed already, we use them as weights and just generate
        # one entry for each bin
        n, bins, patches = ax.hist(bins[:-1], bins=bins, bottom=bottom, weights=y, **kwds)

        cls._update_stacker(ax, stacking_id, n)
        return patches

    def _compute_plot_data(self):
        summary = KoalasHistPlotSummary(self.data, self.data.name)
        # generates a pandas DF with one row for each bin
        self.data = summary.calc_histogram(self.bins)


class KoalasPiePlot(PiePlot, TopNPlot):

    def __init__(self, data, **kwargs):
        super(KoalasPiePlot, self).__init__(self.get_top_n(data), **kwargs)

    def _make_plot(self):
        self.set_result_text(self._get_ax(0))
        super(KoalasPiePlot, self)._make_plot()


class KoalasAreaPlot(AreaPlot, SampledPlot):
    def __init__(self, data, **kwargs):
        super(KoalasAreaPlot, self).__init__(self.get_sampled(data), **kwargs)

    def _make_plot(self):
        self.set_result_text(self._get_ax(0))
        super(KoalasAreaPlot, self)._make_plot()


class KoalasLinePlot(LinePlot, SampledPlot):
    def __init__(self, data, **kwargs):
        super(KoalasLinePlot, self).__init__(self.get_sampled(data), **kwargs)

    def _make_plot(self):
        self.set_result_text(self._get_ax(0))
        super(KoalasLinePlot, self)._make_plot()


class KoalasBarhPlot(BarhPlot, TopNPlot):

    def __init__(self, data, **kwargs):
        super(KoalasBarhPlot, self).__init__(self.get_top_n(data), **kwargs)

    def _make_plot(self):
        self.set_result_text(self._get_ax(0))
        super(KoalasBarhPlot, self)._make_plot()


class KoalasScatterPlot(ScatterPlot, TopNPlot):

    def __init__(self, data, x, y, **kwargs):
        super().__init__(self.get_top_n(data), x, y, **kwargs)

    def _make_plot(self):
        self.set_result_text(self._get_ax(0))
        super(KoalasScatterPlot, self)._make_plot()


_klasses = [
    KoalasHistPlot,
    KoalasBarPlot,
    KoalasBoxPlot,
    KoalasPiePlot,
    KoalasAreaPlot,
    KoalasLinePlot,
    KoalasBarhPlot,
    KoalasScatterPlot,
]
_plot_klass = {getattr(klass, '_kind'): klass for klass in _klasses}


def plot_series(data, kind='line', ax=None,                    # Series unique
                figsize=None, use_index=True, title=None, grid=None,
                legend=False, style=None, logx=False, logy=False, loglog=False,
                xticks=None, yticks=None, xlim=None, ylim=None,
                rot=None, fontsize=None, colormap=None, table=False,
                yerr=None, xerr=None,
                label=None, secondary_y=False,                 # Series unique
                **kwds):
    """
    Make plots of Series using matplotlib / pylab.

    Each plot kind has a corresponding method on the
    ``Series.plot`` accessor:
    ``s.plot(kind='line')`` is equivalent to
    ``s.plot.line()``.

    Parameters
    ----------
    data : Series

    kind : str
        - 'line' : line plot (default)
        - 'bar' : vertical bar plot
        - 'barh' : horizontal bar plot
        - 'hist' : histogram
        - 'box' : boxplot
        - 'kde' : Kernel Density Estimation plot
        - 'density' : same as 'kde'
        - 'area' : area plot
        - 'pie' : pie plot

    ax : matplotlib axes object
        If not passed, uses gca()
    figsize : a tuple (width, height) in inches
    use_index : boolean, default True
        Use index as ticks for x axis
    title : string or list
        Title to use for the plot. If a string is passed, print the string at
        the top of the figure. If a list is passed and `subplots` is True,
        print each item in the list above the corresponding subplot.
    grid : boolean, default None (matlab style default)
        Axis grid lines
    legend : False/True/'reverse'
        Place legend on axis subplots
    style : list or dict
        matplotlib line style per column
    logx : boolean, default False
        Use log scaling on x axis
    logy : boolean, default False
        Use log scaling on y axis
    loglog : boolean, default False
        Use log scaling on both x and y axes
    xticks : sequence
        Values to use for the xticks
    yticks : sequence
        Values to use for the yticks
    xlim : 2-tuple/list
    ylim : 2-tuple/list
    rot : int, default None
        Rotation for ticks (xticks for vertical, yticks for horizontal plots)
    fontsize : int, default None
        Font size for xticks and yticks
    colormap : str or matplotlib colormap object, default None
        Colormap to select colors from. If string, load colormap with that name
        from matplotlib.
    colorbar : boolean, optional
        If True, plot colorbar (only relevant for 'scatter' and 'hexbin' plots)
    position : float
        Specify relative alignments for bar plot layout.
        From 0 (left/bottom-end) to 1 (right/top-end). Default is 0.5 (center)
    table : boolean, Series or DataFrame, default False
        If True, draw a table using the data in the DataFrame and the data will
        be transposed to meet matplotlib's default layout.
        If a Series or DataFrame is passed, use passed data to draw a table.
    yerr : DataFrame, Series, array-like, dict and str
        See :ref:`Plotting with Error Bars <visualization.errorbars>` for
        detail.
    xerr : same types as yerr.
    label : label argument to provide to plot
    secondary_y : boolean or sequence of ints, default False
        If True then y-axis will be on the right
    mark_right : boolean, default True
        When using a secondary_y axis, automatically mark the column
        labels with "(right)" in the legend
    `**kwds` : keywords
        Options to pass to matplotlib plotting method

    Returns
    -------
    axes : :class:`matplotlib.axes.Axes` or numpy.ndarray of them

    Notes
    -----

    - See matplotlib documentation online for more on this subject
    - If `kind` = 'bar' or 'barh', you can specify relative alignments
      for bar plot layout by `position` keyword.
      From 0 (left/bottom-end) to 1 (right/top-end). Default is 0.5 (center)
    """

    # function copied from pandas.plotting._core
    # so it calls modified _plot below

    import matplotlib.pyplot as plt
    if ax is None and len(plt.get_fignums()) > 0:
        ax = _gca()
        ax = MPLPlot._get_ax_layer(ax)
    return _plot(data, kind=kind, ax=ax,
                 figsize=figsize, use_index=use_index, title=title,
                 grid=grid, legend=legend,
                 style=style, logx=logx, logy=logy, loglog=loglog,
                 xticks=xticks, yticks=yticks, xlim=xlim, ylim=ylim,
                 rot=rot, fontsize=fontsize, colormap=colormap, table=table,
                 yerr=yerr, xerr=xerr,
                 label=label, secondary_y=secondary_y,
                 **kwds)


def _plot(data, x=None, y=None, subplots=False,
          ax=None, kind='line', **kwds):
    from databricks.koalas import DataFrame
    # function copied from pandas.plotting._core
    # and adapted to handle Koalas DataFrame and Series

    kind = _get_standard_kind(kind.lower().strip())
    if kind in _all_kinds:
        klass = _plot_klass[kind]
    else:
        raise ValueError("%r is not a valid plot kind" % kind)

    # scatter and hexbin are inherited from PlanePlot which require x and y
    if kind in ('scatter', 'hexbin'):
        plot_obj = klass(data, x, y, subplots=subplots, ax=ax, kind=kind, **kwds)
    else:

        # check data type and do preprocess before applying plot
        if isinstance(data, DataFrame):
            if x is not None:
                data = data.set_index(x)
            # TODO: check if value of y is plottable
            if y is not None:
                data = data[y]

        plot_obj = klass(data, subplots=subplots, ax=ax, kind=kind, **kwds)
    plot_obj.generate()
    plot_obj.draw()
    return plot_obj.result


class KoalasSeriesPlotMethods(PandasObject):
    """
    Series plotting accessor and method.

    Plotting methods can also be accessed by calling the accessor as a method
    with the ``kind`` argument:
    ``s.plot(kind='hist')`` is equivalent to ``s.plot.hist()``
    """

    def __init__(self, data):
        self.data = data

    def __call__(self, kind='line', ax=None,
                 figsize=None, use_index=True, title=None, grid=None,
                 legend=False, style=None, logx=False, logy=False,
                 loglog=False, xticks=None, yticks=None,
                 xlim=None, ylim=None,
                 rot=None, fontsize=None, colormap=None, table=False,
                 yerr=None, xerr=None,
                 label=None, secondary_y=False, **kwds):
        return plot_series(self.data, kind=kind, ax=ax, figsize=figsize,
                           use_index=use_index, title=title, grid=grid,
                           legend=legend, style=style, logx=logx, logy=logy,
                           loglog=loglog, xticks=xticks, yticks=yticks,
                           xlim=xlim, ylim=ylim, rot=rot, fontsize=fontsize,
                           colormap=colormap, table=table, yerr=yerr,
                           xerr=xerr, label=label, secondary_y=secondary_y,
                           **kwds)
    __call__.__doc__ = plot_series.__doc__

    def line(self, x=None, y=None, **kwargs):
        """
        Plot Series or DataFrame as lines.

        This function is useful to plot lines using DataFrame's values
        as coordinates.

        Parameters
        ----------
        x : int or str, optional
            Columns to use for the horizontal axis.
            Either the location or the label of the columns to be used.
            By default, it will use the DataFrame indices.
        y : int, str, or list of them, optional
            The values to be plotted.
            Either the location or the label of the columns to be used.
            By default, it will use the remaining DataFrame numeric columns.
        **kwds
            Keyword arguments to pass on to :meth:`DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or :class:`numpy.ndarray`
            Return an ndarray when ``subplots=True``.

        See Also
        --------
        matplotlib.pyplot.plot : Plot y versus x as lines and/or markers.
        """
        return self(kind="line", x=x, y=y, **kwargs)

    def bar(self, **kwds):
        """
        Vertical bar plot.

        Parameters
        ----------
        `**kwds` : optional
            Additional keyword arguments are documented in
            :meth:`Koalas.Series.plot`.

        Returns
        -------
        axes : :class:`matplotlib.axes.Axes` or numpy.ndarray of them
        """
        return self(kind='bar', **kwds)

    def barh(self, **kwds):
        """
        Make a horizontal bar plot.

        A horizontal bar plot is a plot that presents quantitative data with
        rectangular bars with lengths proportional to the values that they
        represent. A bar plot shows comparisons among discrete categories. One
        axis of the plot shows the specific categories being compared, and the
        other axis represents a measured value.

        Parameters
        ----------
        x : label or position, default DataFrame.index
            Column to be used for categories.
        y : label or position, default All numeric columns in dataframe
            Columns to be plotted from the DataFrame.
        **kwds
            Keyword arguments to pass on to :meth:`databricks.koalas.DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or numpy.ndarray of them

        See Also
        --------
        matplotlib.axes.Axes.bar : Plot a vertical bar plot using matplotlib.

        Examples
        --------
        >>> df = ks.DataFrame({'lab':['A', 'B', 'C'], 'val':[10, 30, 20]})
        >>> plot = df.val.plot.barh()
        """
        return self(kind='barh', **kwds)

    def box(self, **kwds):
        """
        Make a box plot of the DataFrame columns.

        Parameters
        ----------
        `**kwds` : optional
            Additional keyword arguments are documented in
            :meth:`Koalas.Series.plot`.

        `precision`: scalar, default = 0.01
            This argument is used by Koalas to compute approximate statistics
            for building a boxplot. Use *smaller* values to get more precise
            statistics.

        Returns
        -------
        axes : :class:`matplotlib.axes.Axes` or numpy.ndarray of them

        Notes
        -----
        There are behavior differences between Koalas and pandas.

        * Koalas computes approximate statistics - expect differences between
          pandas and Koalas boxplots, especially regarding 1st and 3rd quartiles.
        * The `whis` argument is only supported as a single number.
        * Koalas doesn't support the following argument(s).

          * `bootstrap` argument is not supported
          * `autorange` argument is not supported
        """
        return self(kind='box', **kwds)

    def hist(self, bins=10, **kwds):
        """
        Draw one histogram of the DataFrame’s columns.

        Parameters
        ----------
        bins : integer, default 10
            Number of histogram bins to be used
        `**kwds` : optional
            Additional keyword arguments are documented in
            :meth:`Koalas.Series.plot`.

        Returns
        -------
        axes : :class:`matplotlib.axes.Axes` or numpy.ndarray of them
        """
        return self(kind='hist', bins=bins, **kwds)

    def kde(self, bw_method=None, ind=None, **kwds):
        return _unsupported_function(class_name='pd.Series', method_name='kde')()

    density = kde

    def area(self, **kwds):
        """
        Draw a stacked area plot.

        An area plot displays quantitative data visually.
        This function wraps the matplotlib area function.

        Parameters
        ----------
        x : label or position, optional
            Coordinates for the X axis. By default uses the index.
        y : label or position, optional
            Column to plot. By default uses all columns.
        stacked : bool, default True
            Area plots are stacked by default. Set to False to create a
            unstacked plot.
        **kwds : optional
            Additional keyword arguments are documented in
            :meth:`DataFrame.plot`.

        Returns
        -------
        matplotlib.axes.Axes or numpy.ndarray
            Area plot, or array of area plots if subplots is True.

        Examples
        --------
        >>> df = ks.DataFrame({
        ...     'sales': [3, 2, 3, 9, 10, 6],
        ...     'signups': [5, 5, 6, 12, 14, 13],
        ...     'visits': [20, 42, 28, 62, 81, 50],
        ... }, index=pd.date_range(start='2018/01/01', end='2018/07/01',
        ...                        freq='M'))
        >>> plot = df.sales.plot.area()
        """
        return self(kind='area', **kwds)

    def pie(self, **kwds):
        """
        Generate a pie plot.

        A pie plot is a proportional representation of the numerical data in a
        column. This function wraps :meth:`matplotlib.pyplot.pie` for the
        specified column. If no column reference is passed and
        ``subplots=True`` a pie plot is drawn for each numerical column
        independently.

        Parameters
        ----------
        y : int or label, optional
            Label or position of the column to plot.
            If not provided, ``subplots=True`` argument must be passed.
        **kwds
            Keyword arguments to pass on to :meth:`Koalas.Series.plot`.

        Returns
        -------
        matplotlib.axes.Axes or np.ndarray of them
            A NumPy array is returned when `subplots` is True.

        Examples
        --------
        >>> df = ks.DataFrame({'mass': [0.330, 4.87 , 5.97],
        ...                    'radius': [2439.7, 6051.8, 6378.1]},
        ...                   index=['Mercury', 'Venus', 'Earth'])
        >>> plot = df.mass.plot.pie(figsize=(5, 5))

        >>> plot = df.mass.plot.pie(subplots=True, figsize=(6, 3))
        """
        return self(kind='pie', **kwds)


class KoalasFramePlotMethods(PandasObject):
    # TODO: not sure if Koalas wanna combine plot method for Series and DataFrame
    """
    DataFrame plotting accessor and method.

    Plotting methods can also be accessed by calling the accessor as a method
    with the ``kind`` argument:
    ``df.plot(kind='hist')`` is equivalent to ``df.plot.hist()``
    """
    def __init__(self, data):
        self.data = data

    def __call__(self, x=None, y=None, kind='line', ax=None,
                 subplots=None, sharex=None, sharey=False, layout=None,
                 figsize=None, use_index=True, title=None, grid=None,
                 legend=True, style=None, logx=False, logy=False,
                 loglog=False, xticks=None, yticks=None, xlim=None,
                 ylim=None, rot=None, fontsize=None, colormap=None,
                 table=False, yerr=None, xerr=None, secondary_y=False,
                 sort_columns=False, **kwds):
        return plot_frame(self.data, x=x, y=y, kind=kind, ax=ax,
                          subplots=subplots, sharex=sharex, sharey=sharey, layout=layout,
                          figsize=figsize, use_index=use_index, title=title, grid=grid,
                          legend=legend, style=style, logx=logx, logy=logy,
                          loglog=loglog, xticks=xticks, yticks=yticks, xlim=xlim,
                          ylim=ylim, rot=rot, fontsize=fontsize, colormap=colormap,
                          table=table, yerr=yerr, xerr=xerr, secondary_y=secondary_y,
                          sort_columns=sort_columns, **kwds)

    def line(self, x=None, y=None, **kwargs):
        """
        Plot DataFrame as lines.

        Parameters
        ----------
        x: int or str, optional
            Columns to use for the horizontal axis.
        y : int, str, or list of them, optional
            The values to be plotted.
        **kwargs
            Keyword arguments to pass on to :meth:`DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or :class:`numpy.ndarray`
            Return an ndarray when ``subplots=True``.

        See Also
        --------
        matplotlib.pyplot.plot : Plot y versus x as lines and/or markers.
        """
        return self(kind='line', x=x, y=y, **kwargs)

    def kde(self, bw_method=None, ind=None, **kwds):
        return _unsupported_function(class_name='pd.DataFrame', method_name='kde')()

    def pie(self, y=None, **kwds):
        """
        Generate a pie plot.
        A pie plot is a proportional representation of the numerical data in a
        column. This function wraps :meth:`matplotlib.pyplot.pie` for the
        specified column. If no column reference is passed and
        ``subplots=True`` a pie plot is drawn for each numerical column
        independently.

        Parameters
        ----------
        y : int or label, optional
            Label or position of the column to plot.
            If not provided, ``subplots=True`` argument must be passed.
        **kwds
            Keyword arguments to pass on to :meth:`Koalas.DataFrame.plot`.

        Returns
        -------
        matplotlib.axes.Axes or np.ndarray of them
            A NumPy array is returned when `subplots` is True.
        """
        from databricks.koalas import DataFrame

        # Pandas will raise an error if y is None and subplots if not True
        if (
                isinstance(self.data, DataFrame)
                and y is None
                and not kwds.get("subplots", False)
        ):
            raise ValueError("pie requires either y column or 'subplots=True'")
        return self(kind='pie', y=y, **kwds)

    def area(self, x=None, y=None, stacked=True, **kwds):
        """
        Draw a stacked area plot.

        An area plot displays quantitative data visually.
        This function wraps the matplotlib area function.

        Parameters
        ----------
        x : label or position, optional
            Coordinates for the X axis. By default uses the index.
        y : label or position, optional
            Column to plot. By default uses all columns.
        stacked : bool, default True
            Area plots are stacked by default. Set to False to create a
            unstacked plot.
        **kwds : optional
            Additional keyword arguments are documented in
            :meth:`DataFrame.plot`.

        Returns
        -------
        matplotlib.axes.Axes or numpy.ndarray
            Area plot, or array of area plots if subplots is True.
        """
        return self(kind='area', x=x, y=y, stacked=stacked, **kwds)

    def bar(self, x=None, y=None, **kwds):
        """
        Vertical bar plot.

        Parameters
        ----------
        x : label or position, optional
            Allows plotting of one column versus another.
            If not specified, the index of the DataFrame is used.
        y : label or position, optional
            Allows plotting of one column versus another.
            If not specified, all numerical columns are used.
        `**kwds` : optional
            Additional keyword arguments are documented in
            :meth:`Koalas.DataFrame.plot`.

        Returns
        -------
        axes : :class:`matplotlib.axes.Axes` or numpy.ndarray of them
        """
        return self(kind='bar', x=x, y=y, **kwds)

    def barh(self, x=None, y=None, **kwargs):
        """
        Make a horizontal bar plot.

        A horizontal bar plot is a plot that presents quantitative data with rectangular
        bars with lengths proportional to the values that they represent. A bar plot shows
        comparisons among discrete categories. One axis of the plot shows the specific
        categories being compared, and the other axis represents a measured value.

        Parameters
        ----------
        x : label or position, default DataFrame.index
            Column to be used for categories.
        y : label or position, default All numeric columns in dataframe
            Columns to be plotted from the DataFrame.
        **kwds:
            Keyword arguments to pass on to :meth:`databricks.koalas.DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or numpy.ndarray of them

        See Also
        --------
        matplotlib.axes.Axes.bar : Plot a vertical bar plot using matplotlib.
        """
        return self(kind='barh', x=x, y=y, **kwargs)

    def hexbin(self, bw_method=None, ind=None, **kwds):
        return _unsupported_function(class_name='pd.DataFrame', method_name='hexbin')()

    def density(self, bw_method=None, ind=None, **kwds):
        return _unsupported_function(class_name='pd.DataFrame', method_name='density')()

    def box(self, bw_method=None, ind=None, **kwds):
        return _unsupported_function(class_name='pd.DataFrame', method_name='box')()

    def hist(self, bw_method=None, ind=None, **kwds):
        return _unsupported_function(class_name='pd.DataFrame', method_name='hist')()

    def scatter(self, x, y, s=None, c=None, **kwds):
        """
        Create a scatter plot with varying marker point size and color.

        The coordinates of each point are defined by two dataframe columns and
        filled circles are used to represent each point. This kind of plot is
        useful to see complex correlations between two variables. Points could
        be for instance natural 2D coordinates like longitude and latitude in
        a map or, in general, any pair of metrics that can be plotted against
        each other.

        Parameters
        ----------
        x : int or str
            The column name or column position to be used as horizontal
            coordinates for each point.
        y : int or str
            The column name or column position to be used as vertical
            coordinates for each point.
        s : scalar or array_like, optional
        c : str, int or array_like, optional

        **kwds: Optional
            Keyword arguments to pass on to :meth:`databricks.koalas.DataFrame.plot`.

        Returns
        -------
        :class:`matplotlib.axes.Axes` or numpy.ndarray of them

        See Also
        --------
        matplotlib.pyplot.scatter : Scatter plot using multiple input data
            formats.
        """
        return self(kind="scatter", x=x, y=y, s=s, c=c, **kwds)


def plot_frame(data, x=None, y=None, kind='line', ax=None,
               subplots=None, sharex=None, sharey=False, layout=None,
               figsize=None, use_index=True, title=None, grid=None,
               legend=True, style=None, logx=False, logy=False,
               loglog=False, xticks=None, yticks=None, xlim=None,
               ylim=None, rot=None, fontsize=None, colormap=None,
               table=False, yerr=None, xerr=None, secondary_y=False,
               sort_columns=False, **kwds):
    """
    Make plots of DataFrames using matplotlib / pylab.

    Each plot kind has a corresponding method on the
    ``DataFrame.plot`` accessor:
    ``kdf.plot(kind='line')`` is equivalent to
    ``kdf.plot.line()``.

    Parameters
    ----------
    data : DataFrame

    kind : str
        - 'line' : line plot (default)
        - 'bar' : vertical bar plot
        - 'barh' : horizontal bar plot
        - 'hist' : histogram
        - 'box' : boxplot
        - 'kde' : Kernel Density Estimation plot
        - 'density' : same as 'kde'
        - 'area' : area plot
        - 'pie' : pie plot
        - 'scatter' : scatter plot
    ax : matplotlib axes object
        If not passed, uses gca()
    x : label or position, default None
    y : label, position or list of label, positions, default None
        Allows plotting of one column versus another.
    figsize : a tuple (width, height) in inches
    use_index : boolean, default True
        Use index as ticks for x axis
    title : string or list
        Title to use for the plot. If a string is passed, print the string at
        the top of the figure. If a list is passed and `subplots` is True,
        print each item in the list above the corresponding subplot.
    grid : boolean, default None (matlab style default)
        Axis grid lines
    legend : False/True/'reverse'
        Place legend on axis subplots
    style : list or dict
        matplotlib line style per column
    logx : boolean, default False
        Use log scaling on x axis
    logy : boolean, default False
        Use log scaling on y axis
    loglog : boolean, default False
        Use log scaling on both x and y axes
    xticks : sequence
        Values to use for the xticks
    yticks : sequence
        Values to use for the yticks
    xlim : 2-tuple/list
    ylim : 2-tuple/list
    sharex: bool or None, default is None
        Whether to share x axis or not.
    sharey: bool, default is False
        Whether to share y axis or not.
    rot : int, default None
        Rotation for ticks (xticks for vertical, yticks for horizontal plots)
    fontsize : int, default None
        Font size for xticks and yticks
    colormap : str or matplotlib colormap object, default None
        Colormap to select colors from. If string, load colormap with that name
        from matplotlib.
    colorbar : boolean, optional
        If True, plot colorbar (only relevant for 'scatter' and 'hexbin' plots)
    position : float
        Specify relative alignments for bar plot layout.
        From 0 (left/bottom-end) to 1 (right/top-end). Default is 0.5 (center)
    table : boolean, Series or DataFrame, default False
        If True, draw a table using the data in the DataFrame and the data will
        be transposed to meet matplotlib's default layout.
        If a Series or DataFrame is passed, use passed data to draw a table.
    yerr : DataFrame, Series, array-like, dict and str
        See :ref:`Plotting with Error Bars <visualization.errorbars>` for
        detail.
    xerr : same types as yerr.
    label : label argument to provide to plot
    secondary_y : boolean or sequence of ints, default False
        If True then y-axis will be on the right
    mark_right : boolean, default True
        When using a secondary_y axis, automatically mark the column
        labels with "(right)" in the legend
    sort_columns: bool, default is False
        When True, will sort values on plots.
    `**kwds` : keywords
        Options to pass to matplotlib plotting method

    Returns
    -------
    axes : :class:`matplotlib.axes.Axes` or numpy.ndarray of them

    Notes
    -----

    - See matplotlib documentation online for more on this subject
    - If `kind` = 'bar' or 'barh', you can specify relative alignments
      for bar plot layout by `position` keyword.
      From 0 (left/bottom-end) to 1 (right/top-end). Default is 0.5 (center)
    """

    return _plot(data, kind=kind, x=x, y=y, ax=ax,
                 figsize=figsize, use_index=use_index, title=title,
                 grid=grid, legend=legend, subplots=subplots,
                 style=style, logx=logx, logy=logy, loglog=loglog,
                 xticks=xticks, yticks=yticks, xlim=xlim, ylim=ylim,
                 rot=rot, fontsize=fontsize, colormap=colormap, table=table,
                 yerr=yerr, xerr=xerr, sharex=sharex, sharey=sharey,
                 secondary_y=secondary_y, layout=layout, sort_columns=sort_columns,
                 **kwds)

Actually the usage of `_InternalFrame` with `_scol` is for `Series`.