matplotlib colorbars and its text labels

Question

I d like to create a colorbar legend for a heatmap  such that the labels are in the center of each discrete color  Example borrowed from here   import matplotlib pyplot as plt import numpy as np from matplotlib colors import ListedColormap   discrete color scheme cMap   ListedColormap   white    green    blue   red      data np random seed 42  data   np random rand 4  4  fig  ax   plt subplots   heatmap   ax pcolor data  cmap cMap    legend cbar   plt colorbar heatmap  cbar ax set yticklabels   0   1   2    gt 3    cbar set label    of contacts   rotation 270     put the major ticks at the middle of each cell ax set xticks np arange data shape 1     0 5  minor False  ax set yticks np arange data shape 0     0 5  minor False  ax invert yaxis     labels column labels   list  ABCD   row labels   list  WXYZ   ax set xticklabels column labels  minor False  ax set yticklabels row labels  minor False   plt show     This generates the following plot     Ideally I d like to generate a legend bar which has the four colors and for each color  a label in its center  0 1 2  gt 3  How can this be achieved

User · Answer

To add to tacaswell s answer  the colorbar   function has an optional cax input you can use to pass an axis on which the colorbar should be drawn   If you are using that input  you can directly set a label using that axis   import matplotlib pyplot as plt from mpl toolkits axes grid1 import make axes locatable  fig  ax   plt subplots   heatmap   ax imshow data  divider   make axes locatable ax  cax   divider append axes  bottom   size  10    pad 0 6  cb   fig colorbar heatmap  cax cax  orientation  horizontal    cax set xlabel  data label      cax    cb ax

User · Answer

import matplotlib pyplot as plt import numpy as np from matplotlib colors import ListedColormap   discrete color scheme cMap   ListedColormap   white    green    blue   red      data np random seed 42  data   np random rand 4  4  fig  ax   plt subplots   heatmap   ax pcolor data  cmap cMap    legend cbar   plt colorbar heatmap   cbar ax get yaxis   set ticks     for j  lab in enumerate    0     1     2      gt 3          cbar ax text  5   2   j   1    8 0  lab  ha  center   va  center   cbar ax get yaxis   labelpad   15 cbar ax set ylabel    of contacts   rotation 270      put the major ticks at the middle of each cell ax set xticks np arange data shape 1     0 5  minor False  ax set yticks np arange data shape 0     0 5  minor False  ax invert yaxis     labels column labels   list  ABCD   row labels   list  WXYZ   ax set xticklabels column labels  minor False  ax set yticklabels row labels  minor False   plt show     You were very close   Once you have a reference to the color bar axis  you can do what ever you want to it  including putting text labels in the middle   You might want to play with the formatting to make it more visible

[python] matplotlib: colorbars and its text labels

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