seaborn heatmap color scheme based on row values

Question

I have a dataframe, reproduced partly as such:

import pandas as pd
import numpy as np
tab = pd.DataFrame(np.array([[ 46,  39,  25,  29,  21,  12,  33,  32,  70, 109, 144, 158, 161,
    184, 163, 113, 117,  82,  76,  88,  77,  76,  64,  35],
   [ 39,  33,  29,  29,  26,  14,  25,  33,  60,  83, 126, 117, 111,
    148, 141, 104,  92,  75,  78,  74,  63,  67,  52,  39],
   [ 30,  27,  14,  11,  20,  17,  21,  31,  48,  62,  83,  78,  88,
     90,  80,  67,  53,  61,  47,  54,  50,  48,  35,  26],
   [ 30,  24,  19,  15,  17,  10,  12,  18,  34,  69,  88,  79, 109,
     95,  89,  82,  53,  46,  53,  57,  39,  41,  26,  29],
   [ 37,  31,  18,  12,  30,  13,  15,  19,  51,  61,  74,  81,  77,
    100,  96,  74,  60,  57,  42,  48,  43,  40,  29,  25],
   [ 14,   8,  14,  11,  13,   7,   9,  15,  42,  49,  50,  44,  53,
     42,  31,  31,  30,  27,  33,  25,  27,  17,  20,  17],
   [ 10,  15,   6,  10,  15,  11,   7,  18,  28,  43,  49,  37,  41,
     33,  37,  32,  26,  28,  19,  24,  19,  19,  13,  18],
   [  9,   9,   8,  12,   7,  11,   4,   8,  14,  15,  23,  30,  29,
     34,  25,  39,  22,  20,  15,  23,  12,  19,  14,  13],
   [  0,   3,   4,   1,   1,   0,   3,   4,   4,   5,   3,   5,   6,
      7,   3,   3,   6,   4,   2,   3,   3,   2,   2,   2],
   [  3,   0,   1,   0,   0,   0,   1,   1,   4,   8,   2,   4,   7,
      2,   2,   9,   3,   5,   1,   5,   2,   0,   4,   1]]), index = 
        ['Stadsdeel Zuid', 'Stadsdeel West', 'Stadsdeel Nieuw-West',
   'Stadsdeel Centrum', 'Stadsdeel Oost', 'Stadsdeel Noord',
   'Wijk 00 Amstelveen', 'Stadsdeel Zuidoost', 'Wijk 00',
   'Wijk 00 Aalsmeer'])

and I created a heatmap as such

ax = sns.heatmap(tab, linewidths=.5 ,robust=True ,annot_kws = {'size':14})
ax.tick_params(labelsize=14)
ax.figure.set_size_inches((12, 10))

I would like though that values to anchor the colormap are based on min-max values per row so that also rows with lower values are well visible. (in reality the table contains many more rows with low values that the heatmap barely shows color-wise)

How to achieve this ?

Springe

Please post some raw data of your original dataset so we can reproduce you problem. It's hard to copy and paste data from images. – Gal

you are right. See updated answer – Springe

Sounds like you want to normalize the rows? – Sorehead

Answer 1

I would normalize the tab rows by the maximum value in each row with:

tab_n = tab.div(tab.max(axis=1), axis=0)

where tab_n is the normalized tab having values in the range [0,1]. Hope that helps. Plotting tab_n should return an heatmap like this:

Gal

as easy as that. great. – Springe

I have a AttributeError: 'numpy.ndarray' object has no attribute 'div' Do you have an idea ? – Dowlen

@JohanC still getting the same error using true_divide – Bicarb

@ranbar If tab is a 2D numpy array (instead of a dataframe), you can try tab_n = tab / tab.max(axis=1, keepdims=True) – Suprarenal