How do I assign multiple labels at once in matplotlib?

Question

I have the following dataset:

x = [0, 1, 2, 3, 4]
y = [ [0, 1, 2, 3, 4],
      [5, 6, 7, 8, 9],
      [9, 8, 7, 6, 5] ]

Now I plot it with:

Answer 1

I used the following to show labels for a dataframe without using the dataframe plot:

lines_ = plot(df)
legend(lines_, df.columns) # df.columns is a list of labels

Answer 2

It is not possible to plot those two arrays agains each other directly (with at least version 1.1.1), therefore you must be looping over your y arrays. My advice would be to loop over the labels at the same time:

import matplotlib.pyplot as plt

x = [0, 1, 2, 3, 4]
y = [ [0, 1, 2, 3, 4], [5, 6, 7, 8, 9], [9, 8, 7, 6, 5] ]
labels = ['foo', 'bar', 'baz']

for y_arr, label in zip(y, labels):
    plt.plot(x, y_arr, label=label)

plt.legend()
plt.show()

Edit: @gcalmettes pointed out that as numpy arrays, it is possible to plot all the lines at the same time (by transposing them). See @gcalmettes answer & comments for details.

Answer 3

If you're using a DataFrame, you can also iterate over the columns of the data you want to plot:

# Plot figure
fig, ax = plt.subplots(figsize=(5,5))
# Data
data = data
# Plot
for i in data.columns:
    _ = ax.plot(data[i], label=i)
    _ = ax.legend() 
plt.show()