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A pie chart represents numerical proportions as slices of a pie. The size of a slice is proportional to the quantity it represents. Each slice usually has a different color.
NOTE: It is often better to use bar charts instead of pie charts, for example because comparing the sizes of two circular sectors in a pie chart can be more challenging than comparing the sizes of two bars in a bar chart.
Let's study this potential problem in a future activity. For now, let's implement a function to create simple pie charts!
Our function has the following signature:
def pie_chart(
values: list[float], colors: list[Color], radius: float
) -> Graphic:
It takes the following parameters:
In the end, you should be able to call it like this:
show_graphic(pie_chart([1.0, 2.0, 3.0], [red, green, blue], 100))
This call should produce the following chart:
A pie chart is made up of slices, one slice per value. Each slice is a circular sector.
You can use the circular_sector function to create a sector.
Check out the API (by hovering over the red word) to figure out where the pinning position of a circular sector is located. Use that fact for rotating and composing multiple circular sectors into a pie.
Now let's use your function for a slightly more complex pie chart. To be able to clearly distinguish the different pieces in a categorical visualizations (e.g., the different slices in a pie chart), picking a set of colors that are easily distinguishable is a good idea. The Color Brewer is a great resource to create such color palettes. Here we include a palette that is optimized for visualizing 10 different categories.
Note that in the code below, the number of values and the number of colors differ.
Your pie_chart
function should be able to deal with this situation.
It should cycle through the given number of colors:
If there are fewer values than colors,
it should use the first N colors.
If there are more values than colors,
it should cycle through colors reusing the same color for multiple slices.
You learned how to compose multiple circular sectors into a pie chart. You also learned about good color palettes for qualitative / categorical visualizations.
This activity has been created by LuCE Research Lab and is licensed under CC BY-SA 4.0.
Simple Pie Chart
PyTamaro is a project created by the Lugano Computing Education Research Lab at the Software Institute of USI
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