How to make two lines use the same color and legend label in matplotlib?-CodePudding

let's say I have two sets of data to plot, x1 vs. y1, and x2 vs. y2. Where we can take the x variables as vectors of time, and y a matrix with the same number of rows as x, and 5 columns, each column being its individual line:

for i in range(5):
    plt.plot(x1,y1[:,i],x2,y2[:,i],label=labels[i])
plt.legend()

This results in each line being given a different color, and an individual label, where each label is repeated once. How can I have the data on each iteration in the for loop being plotted with the same color, and juts one label?

Thanks!

CodePudding user response：

There are many ways to accomplish what you are asking.

Here is a simple approach which uses the automatic coloring scheme for the first line, and extracts its color to asign to the second line. Only the first line gets a label for the legend.

for i in range(5):
    line, = plt.plot(x1, y1[i, :], label=f'label {i}')
    plt.plot(x2, y2[i, :], color=line.get_color())
plt.legend()

CodePudding user response：

You can define colours by the c parameter in plt.plot. If you set this all to the same colour, every line will be the same colour:

c = "#000000"
for i in range(5):
    plt.plot(x1,y1[:,i],x2,y2[:,i],label=labels[i], c=c)
plt.legend()

Now for the labels, in order to have 1 label for all lines, you can only just label one line. This can be done by:

c = "#000000"
label = "Same label"
for i in range(5):
    if i == 0:
        plt.plot(x1,y1[:,i],x2,y2[:,i],label=label, c=c)
    else:
        plt.plot(x1,y1[:,i],x2,y2[:,i], c=c)
plt.legend()

This should make all lines the same colour (black in this case) and the label Same label only occurs once in the legend.