Negative values in pie charts

chartsgraphpie-chartvisualization

My application visualizes data using a variety of chart types. Some data visualized by a pie chart includes negative values. Pie charts aren't designed to display negatives.

Excel outputs the absolute value of all values. So, -20 is output in the pie chart as a slice with 20% of the pie's circumference. The only way to tell the number is negative is to reference the legend.

Highcharts, which is the charting engine we use, leaves the positive slices intact, but renders the negatives in a very odd and confusing way (Example on JS Lint). Props to them for trying to render negatives, but our users are confused.

Others have suggested filtering out the negatives altogether, since they don't make sense on a pie chart. This strips data and doesn't wholly represent the data set, so it probably won't work for us.

And, others have suggested using a more appropriate chart type, such as a bar chart.

Any other options for solving this? How have you done it?

Best Answer

Use shades of green for positive values.

Use the absolute value of your negative values to then display different negative values in shades of red.

Related Solutions

Matplotlib – How to add a legend to matplotlib pie chart

I checked your code, and the plt.legend() creates a legend, just how you want it to be; maybe set the loc="lower left", so it does not overlap with the relevant pieces of pie.

For me, the strings are displayed properly, besides the non standard chars - which might cause the problem that they are not displayed to you at all. Only the biggest slice and "Otros" do not contain special chars. Maybe also try to resize the figure, as they might be pushed out of the canvas. Please refer to how to write accents with matplotlib and try again with proper strings.

The percentages are not shown, because you did not set them to be shown. Please refer to the example posted by you, as you omitted autopct='%1.1f%%'which will plot the percentages. In this special case, I would rather not plot the percentages, as they will overlap just like the labels on the border, as some slices are too small. Maybe add these information to the legend.

Putting it all together (besides the special chars - I had some problems activating TeX), try the following code:

# -*- coding: UTF-8 -*-
import matplotlib.pyplot as plt
# The slices will be ordered and plotted counter-clockwise.
labels = [r'Rayos X (88.4 %)', r'RMN en solucion (10.6 %)', 
r'Microscopia electronica (0.7 %)', r'Otros (0.3 %)']
sizes = [88.4, 10.6, 0.7, 0.3]
colors = ['yellowgreen', 'gold', 'lightskyblue', 'lightcoral']
patches, texts = plt.pie(sizes, colors=colors, startangle=90)
plt.legend(patches, labels, loc="best")
# Set aspect ratio to be equal so that pie is drawn as a circle.
plt.axis('equal')
plt.tight_layout()
plt.show()

resulting pie chart

Best Answer

Related Solutions

Matplotlib – How to add a legend to matplotlib pie chart

Related Topic