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Line Graphs in Matplotlib
Legends

When we have multiple lines on a single graph we can label them by using the command plt.legend().

The legend method takes a list with the labels to display. So, for example, we can call:

plt.plot([0, 1, 2, 3, 4], [0, 1, 4, 9, 16]) plt.plot([0, 1, 2, 3, 4], [0, 1, 8, 27, 64]) plt.legend(['parabola', 'cubic']) plt.show()

which would display a legend on our graph, labeling each line: legend

plt.legend() can also take a keyword argument loc, which will position the legend on the figure.

These are the position values loc accepts:

Number Code String
0 best
1 upper right
2 upper left
3 lower left
4 lower right
5 right
6 center left
7 center right
8 lower center
9 upper center
10 center

Note: If you decide not to set a value for loc, it will default to choosing the “best” location.

For, example, we can call plt.legend() and set loc to 6:

plt.legend(['parabola', 'cubic'], loc=6) plt.show()

which would move the legend to the left side of the graph: legend_loc

Sometimes, it’s easier to label each line as we create it. If we want, we can use the keyword label inside of plt.plot(). If we choose to do this, we don’t pass any labels into plt.legend(). For example:

plt.plot([0, 1, 2, 3, 4], [0, 1, 4, 9, 16], label="parabola") plt.plot([0, 1, 2, 3, 4], [0, 1, 8, 27, 64], label="cubic") plt.legend() # Still need this command! plt.show()

This would display a legend that looks just like what we had before: legend

Instructions

1.

We have plotted three lines for you. They represent the temperatures over the past year in three locations:

  • Hyrule (hyrule)
  • Kakariko (kakariko)
  • Gerudo Valley (gerudo)

Create a list of strings containing "Hyrule", "Kakariko", and "Gerudo Valley", and store it in a variable called legend_labels.

2.

Create a legend for the graph by feeding in legend_labels into plt.legend().

3.

Set the legend to be at the lower center of the chart.

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