How to change bar color based on number value in matplotlib-CodePudding

I have a horizontal bar chart where I'm supposed to turn the bars slowly from yellow to red based on the horizontal value. So the greater the X value the more the bars chart get red

(I wanted to show the plot but I couldn't upload the image of it due to my low reputation)

import matplotlib.pyplot as plt 

x = [3,3,4]
y = [1,2,5]
plt.barh(x,y)
plt.show()

CodePudding user response：

I'd do something of similar, hand-made:

colorsValue = []
for value in x:
    if value < LOW_TRESHOLD:
        colorsValue.append('yellow')
    elif value >= HIGH_TRESHOLD:
        colorsValue.append('red')
    else:
        colorsValue.append('orange')

plt.barh(x, y, color = colorsValue)

where LOW_TRESHOLD and HIGH_TRESHOLD are values decided by you, as well as colors. List of matplotlib colors is here.

This was only a minimal example to show you the syntax. Solution of Kroshtan is good as well and more general than my home-made solution, so I advice you to use his one.

CodePudding user response：

You can pass an array in the color parameter. The values of this array can be calculated using cmap from the matplotlib documentation.

colors = [(1, 1, 0), (1, 0, 0)]
my_cmap = LinearSegmentedColormap.from_list(
    'color_map', colors, N=100)

Then you scale the colors to the values you have:

rescale = lambda y: (y - np.min(y)) / (np.max(y) - np.min(y))    
plt.barh(x,y,color=my_cmap(rescale(y)))
plt.show()