'P-P plot of the percentiles (probabilities) of x versus the
probabilities (percetiles) of a distribution.
Parameters
xlabel, ylabel : str or None, optional
User-provided lables for the x-axis and y-axis. If None (default),
other values are used depending on the status of the kwarg `other`.
line : str {\'45\', \'s\', \'r\', q\'} or None, optional
Options for the reference line to which the data is compared:
- \'45\' - 45-degree line
- \'s\' - standardized line, the expected order statistics are scaled
by the standard deviation of the given sample and have the mean
added to them
- \'r\' - A regression line is fit
- \'q\' - A line is fit through the quartiles.
- None - by default no reference line is added to the plot.
other : `ProbPlot` instance, array-like, or None, optional
If provided, the sample quantiles of this `ProbPlot` instance are
plotted against the sample quantiles of the `other` `ProbPlot`
instance. If an array-like object is provided, it will be turned
into a `ProbPlot` instance using default parameters. If not provided
(default), the theoretical quantiles are used.
ax : Matplotlib AxesSubplot instance, optional
If given, this subplot is used to plot in instead of a new figure
being created.
**plotkwargs : additional matplotlib arguments to be passed to the
`plot` command.
Returns
fig : Matplotlib figure instance
If `ax` is None, the created figure.  Otherwise the figure to which
`ax` is connected.'

def ppplot(self, xlabel=None, ylabel=None, line=None, other=None, ax=None, **plotkwargs):

    if (other is not None):
        check_other = isinstance(other, ProbPlot)
        if (not check_other):
            other = ProbPlot(other)
        (fig, ax) = _do_plot(other.sample_percentiles, self.sample_percentiles, self.dist, ax=ax, line=line, **plotkwargs)
        if (xlabel is None):
            xlabel = 'Probabilities    of    2nd    Sample'
        if (ylabel is None):
            ylabel = 'Probabilities    of    1st    Sample'
    else:
        (fig, ax) = _do_plot(self.theoretical_percentiles, self.sample_percentiles, self.dist, ax=ax, line=line, **plotkwargs)
        if (xlabel is None):
            xlabel = 'Theoretical    Probabilities'
        if (ylabel is None):
            ylabel = 'Sample    Probabilities'
    ax.set_xlabel(xlabel)
    ax.set_ylabel(ylabel)
    ax.set_xlim([0.0, 1.0])
    ax.set_ylim([0.0, 1.0])
    return fig
