Conditional formatting for 2- or 3-scale coloring of cells of a table

问题

I would like to output a simple table to a PDF file with some conditional formatting of 2- or 3-scale coloring of cells dependent on the value. Like the red-white-green color scaling in Microsoft Excel conditional formatting option.

import pandas
import numpy as np
df = pandas.DataFrame(np.random.randn(10, 2), columns=list('ab'))
print df

#Output:
          a         b
0 -1.625192 -0.949186
1 -0.089884  0.825922
2  2.117651 -0.046258
3 -0.921751 -0.144447
4 -0.294095 -1.774725
5 -0.780523 -0.435909
6  0.544958  0.303268
7  0.014335  0.036182
8 -0.756565  0.120711
9  1.145055  0.542755

Now, I would like to output this to a PDF in a table with a 3-scale conditional format for column a and independently for column b so my output would look like the below example from Excel.

Kind of like this, but by column: enter image description here

回答1:

Ok, I did a little more research and this pretty much covers what i wanted to do. using matplotlib colormaps did the trick. here is a link to the options of map colours. matplotlib color maps

I went with RdYlGn colouring.

import pandas as pd
import numpy as np
from matplotlib import pyplot as plt

df = pd.DataFrame(np.random.randn(10, 8), columns=list('abcdefgh'))

print df

#Round to two digits to print nicely
vals = np.around(df.values, 2)
#Normalize data to [0, 1] range for color mapping below
normal = (df - df.min()) / (df.max() - df.min())

fig = plt.figure()
ax = fig.add_subplot(111)
ax.axis('off')
the_table=ax.table(cellText=vals, rowLabels=df.index, colLabels=df.columns, 
                   loc='center', cellColours=plt.cm.RdYlGn(normal),animated=True)
fig.savefig("table.png")

Output:

回答2:

I arrive here looking for a way to make conditional formatting with a table (not to print it on PDF). Anyway, In case that your interested in pandas has a styling module to output enhanced table coloring

import seaborn as sns

cm = sns.light_palette("green", as_cmap=True)
df.style.background_gradient(cmap = cm)

来源：https://stackoverflow.com/questions/17748570/conditional-formatting-for-2-or-3-scale-coloring-of-cells-of-a-table

标签

python

numpy

matplotlib

pandas