Stacked data modification (matplotlib)

Question

I have a dataset and want to visualize a horizontal stacked bar.

The problem is, each data columns of Promotors, Neutrals, and detractors, corresponding to each year (e.g., first, second, and so on) is meant to be 100 (e.g., sum of 21, 46.5, and 32.5 should be 100). However, my visualization result shows that it does not stack to 100.

Any advices? Thanks!

from matplotlib import pyplot as plt

plt.rcParams["figure.figsize"] = [10, 8]
       
year = ['first', 'second', 'third', 'fourth', 'fifth', 'sixth']
promoters = [21, 20.8, 21.8,27,24,20.5]
neutrals = [46.5, 56.0, 54.3,47.8,50.0,52.5]
detractors = [32.5, 23.3, 24.0,25.3,26.0,27.0]

b1 = plt.barh(year, promoters, color="darkseagreen")
b2 = plt.barh(year, neutrals, left=promoters, color="lightyellow")
b3 = plt.barh(year, detractors, left=neutrals, color="coral")


plt.legend([b1, b2, b3], ["promoters", "neutrals", "detractors"], loc="upper right")
plt.xlim([0, 100])

plt.show

There are several ways you could solve it (add a "unknown" component, or normalize the sum to 100, or something) but the solution is dependant on WHY the numbers don't add up to 100. So this is not really a programming question, but rather a data presentation or visualization question. I think the quesitons fits better in other SE sites, such as https://datascience.stackexchange.com/ — LudvigH, Apr 19 '22 at 08:04

score 1 · Answer 1 · answered Apr 19 '22 at 08:15

sorry, I am not good at English, So I can't really explain it, but I'll put my code here, hopefully you can understand it.

from matplotlib import pyplot as plt
import numpy as np


plt.rcParams["figure.figsize"] = [10, 8]

year = ['first', 'second', 'third', 'fourth', 'fifth', 'sixth']
promoters = [21, 20.8, 21.8, 27, 24, 20.5]
neutrals = [46.5, 56.0, 54.3, 47.8, 50.0, 52.5]
detractors = [32.5, 23.3, 24.0, 25.3, 26.0, 27.0]

"""
This is my code
"""
# The starting point of b3 
detractors_left_arry = np.sum([promoters, neutrals], axis=0).tolist()
print(detractors_left_arry)

b1 = plt.barh(year, promoters, color="darkseagreen")
b2 = plt.barh(year, neutrals, left=promoters, color="lightyellow")
# b3 = plt.barh(year, detractors, left=neutrals, color="coral")
b3 = plt.barh(year, detractors, left=detractors_left_arry, color="coral")

plt.legend([b1, b2, b3], ["promoters", "neutrals", "detractors_left_arry"],                 
loc="upper right")
plt.xlim([0, 100])

plt.show()

score 0 · Answer 2 · answered Apr 19 '22 at 08:05

0

The problem is that you are using the wrong reference in the last plt.barh command. The third bar must start at the end of the second one, so you need to sum the first and second values:

from matplotlib import pyplot as plt
       
year = ['first', 'second', 'third', 'fourth', 'fifth', 'sixth']
promoters = [21, 20.8, 21.8,27,24,20.5]
neutrals = [46.5, 56.0, 54.3,47.8,50.0,52.5]
detractors = [32.5, 23.3, 24.0,25.3,26.0,27.0]

plt.figure()
b1 = plt.barh(year, promoters, color="darkseagreen")
b2 = plt.barh(year, neutrals, left=promoters, color="lightyellow")
b3 = plt.barh(year, detractors, left=[t1 + t2 for t1, t2 in zip(promoters, neutrals)], color="coral")

plt.legend([b1, b2, b3], ["promoters", "neutrals", "detractors"], loc="upper right")
plt.xlim([0, 100])

plt.show()

answered Apr 19 '22 at 08:05

Davide_sd

10,578
3
18
30

This works really well Thank you! – opsv Apr 19 '22 at 08:11
Is it also possble to locate each value as label inside the bar? – opsv Apr 19 '22 at 08:11
Great. Don't forget to mark this answer as the solution to the question. :) Don't know about that last question... – Davide_sd Apr 19 '22 at 08:12
Do you want to create something like this? https://stackoverflow.com/questions/54162981/how-to-display-data-values-in-stacked-horizontal-bar-chart-in-matplotlib – Davide_sd Apr 19 '22 at 08:14

Stacked data modification (matplotlib)

2 Answers2