content: #-----------------------------------------------------------------------------
  # Copyright (c) 2012 - 2019, Anaconda, Inc., and Bokeh Contributors.
  # All rights reserved.
  #
  # The full license is in the file LICENSE.txt, distributed with this software.
  #-----------------------------------------------------------------------------
  ''' Functions useful for dealing with hexagonal tilings.
  
  For more information on the concepts employed here, see this informative page
  
      https://www.redblobgames.com/grids/hexagons/
  
  '''
  
  #-----------------------------------------------------------------------------
  # Boilerplate
  #-----------------------------------------------------------------------------
  from __future__ import absolute_import, division, print_function, unicode_literals
  
  import logging
  log = logging.getLogger(__name__)
  
  #-----------------------------------------------------------------------------
  # Imports
  #-----------------------------------------------------------------------------
  
  # Standard library imports
  
  # External imports
  import numpy as np
  
  # Bokeh imports
  from .dependencies import import_required
  
  #-----------------------------------------------------------------------------
  # Globals and constants
  #-----------------------------------------------------------------------------
  
  __all__ = (
      'axial_to_cartesian',
      'cartesian_to_axial',
      'hexbin',
  )
  
  #-----------------------------------------------------------------------------
  # General API
  #-----------------------------------------------------------------------------
  
  def axial_to_cartesian(q, r, size, orientation, aspect_scale=1):
      ''' Map axial *(q,r)* coordinates to cartesian *(x,y)* coordinates of
      tiles centers.
  
      This function can be useful for positioning other Bokeh glyphs with
      cartesian coordinates in relation to a hex tiling.
  
      This function was adapted from:
  
          https://www.redblobgames.com/grids/hexagons/#hex-to-pixel
  
      Args:
          q (array[float]) :
              A NumPy array of q-coordinates for binning
  
          r (array[float]) :
              A NumPy array of r-coordinates for binning
  
          size (float) :
              The size of the hexagonal tiling.
  
              The size is defined as the distance from the center of a hexagon
              to the top corner for "pointytop" orientation, or from the center
              to a side corner for "flattop" orientation.
  
          orientation (str) :
              Whether the hex tile orientation should be "pointytop" or
              "flattop".
  
          aspect_scale (float, optional) :
              Scale the hexagons in the "cross" dimension.
  
              For "pointytop" orientations, hexagons are scaled in the horizontal
              direction. For "flattop", they are scaled in vertical direction.
  
              When working with a plot with ``aspect_scale != 1``, it may be
              useful to set this value to match the plot.
  
      Returns:
          (array[int], array[int])
  
      '''
      if orientation == "pointytop":
          x = size * np.sqrt(3) * (q + r/2.0) / aspect_scale
          y = -size * 3/2.0 * r
      else:
          x = size * 3/2.0 * q
          y = -size * np.sqrt(3) * (r + q/2.0) * aspect_scale
  
      return (x, y)
  
  def cartesian_to_axial(x, y, size, orientation, aspect_scale=1):
      ''' Map Cartesion *(x,y)* points to axial *(q,r)* coordinates of enclosing
      tiles.
  
      This function was adapted from:
  
          https://www.redblobgames.com/grids/hexagons/#pixel-to-hex
  
      Args:
          x (array[float]) :
              A NumPy array of x-coordinates to convert
  
          y (array[float]) :
              A NumPy array of y-coordinates to convert
  
          size (float) :
              The size of the hexagonal tiling.
  
              The size is defined as the distance from the center of a hexagon
              to the top corner for "pointytop" orientation, or from the center
              to a side corner for "flattop" orientation.
  
          orientation (str) :
              Whether the hex tile orientation should be "pointytop" or
              "flattop".
  
          aspect_scale (float, optional) :
              Scale the hexagons in the "cross" dimension.
  
              For "pointytop" orientations, hexagons are scaled in the horizontal
              direction. For "flattop", they are scaled in vertical direction.
  
              When working with a plot with ``aspect_scale != 1``, it may be
              useful to set this value to match the plot.
  
      Returns:
          (array[int], array[int])
  
      '''
      HEX_FLAT = [2.0/3.0, 0.0, -1.0/3.0, np.sqrt(3.0)/3.0]
      HEX_POINTY = [np.sqrt(3.0)/3.0, -1.0/3.0, 0.0, 2.0/3.0]
  
      coords = HEX_FLAT if orientation == 'flattop' else HEX_POINTY
  
      x =  x / size * (aspect_scale if orientation == "pointytop" else 1)
      y = -y / size / (aspect_scale if orientation == "flattop" else 1)
  
      q = coords[0] * x + coords[1] * y
      r = coords[2] * x + coords[3] * y
  
      return _round_hex(q, r)
  
  def hexbin(x, y, size, orientation="pointytop", aspect_scale=1):
      ''' Perform an equal-weight binning of data points into hexagonal tiles.
  
      For more sophisticated use cases, e.g. weighted binning or scaling
      individual tiles proportional to some other quantity, consider using
      HoloViews.
  
      Args:
          x (array[float]) :
              A NumPy array of x-coordinates for binning
  
          y (array[float]) :
              A NumPy array of y-coordinates for binning
  
          size (float) :
              The size of the hexagonal tiling.
  
              The size is defined as the distance from the center of a hexagon
              to the top corner for "pointytop" orientation, or from the center
              to a side corner for "flattop" orientation.
  
          orientation (str, optional) :
              Whether the hex tile orientation should be "pointytop" or
              "flattop". (default: "pointytop")
  
          aspect_scale (float, optional) :
              Match a plot's aspect ratio scaling.
  
              When working with a plot with ``aspect_scale != 1``, this
              parameter can be set to match the plot, in order to draw
              regular hexagons (instead of "stretched" ones).
  
              This is roughly equivalent to binning in "screen space", and
              it may be better to use axis-aligned rectangular bins when
              plot aspect scales are not one.
  
      Returns:
          DataFrame
  
          The resulting DataFrame will have columns *q* and *r* that specify
          hexagon tile locations in axial coordinates, and a column *counts* that
          provides the count for each tile.
  
      .. warning::
          Hex binning only functions on linear scales, i.e. not on log plots.
  
      '''
      pd = import_required('pandas','hexbin requires pandas to be installed')
  
      q, r = cartesian_to_axial(x, y, size, orientation, aspect_scale=aspect_scale)
  
      df = pd.DataFrame(dict(r=r, q=q))
      return df.groupby(['q', 'r']).size().reset_index(name='counts')
  
  #-----------------------------------------------------------------------------
  # Dev API
  #-----------------------------------------------------------------------------
  
  #-----------------------------------------------------------------------------
  # Private API
  #-----------------------------------------------------------------------------
  
  def _round_hex(q, r):
      ''' Round floating point axial hex coordinates to integer *(q,r)*
      coordinates.
  
      This code was adapted from:
  
          https://www.redblobgames.com/grids/hexagons/#rounding
  
      Args:
          q (array[float]) :
              NumPy array of Floating point axial *q* coordinates to round
  
          r (array[float]) :
              NumPy array of Floating point axial *q* coordinates to round
  
      Returns:
          (array[int], array[int])
  
      '''
      x = q
      z = r
      y = -x-z
  
      rx = np.round(x)
      ry = np.round(y)
      rz = np.round(z)
  
      dx = np.abs(rx - x)
      dy = np.abs(ry - y)
      dz = np.abs(rz - z)
  
      cond = (dx > dy) & (dx > dz)
      q = np.where(cond              , -(ry + rz), rx)
      r = np.where(~cond & ~(dy > dz), -(rx + ry), rz)
  
      return q.astype(int), r.astype(int)
  
  #-----------------------------------------------------------------------------
  # Code
  #-----------------------------------------------------------------------------
  