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pythonmatplotlibscatter-plot

Scatter plot change color based on value on list

I'm quite new to matplotlib and i would like to know how we can change color of points on a scatter plot based on the value in a list.

In fact, I have a 2-D array that I want to plot and a list with the same number of rows containing, for each point, the color we want to use.

#Example
data = np.array([4.29488806,-5.34487081],
[3.63116248,-2.48616998],
[-0.56023222,-5.89586997],
[-0.51538502,-2.62569576],
[-4.08561754,-4.2870525 ],
[-0.80869722,10.12529582])
colors = ['red','red','red','blue','red','blue']
ax1.plot(data[:,0],data[:,1],'o',picker=True)

How to set the color parameter to fit my list of colors ?

Solution

  • Using a line plot plt.plot()

    plt.plot() does only allow for a single color. So you may simply loop over the data and colors and plot each point individually.

    import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
data = np.array([[4.29488806,-5.34487081],
                [3.63116248,-2.48616998],
                [-0.56023222,-5.89586997],
                [-0.51538502,-2.62569576],
                [-4.08561754,-4.2870525 ],
                [-0.80869722,10.12529582]])
colors = ['red','red','red','blue','red','blue']
for xy, color in zip(data, colors):
    ax.plot(xy[0],xy[1],'o',color=color, picker=True)
    
plt.show()

    enter image description here

    Using scatter plot plt.scatter()

    In order to produce a scatter plot, use scatter. This has an argument c, which allows numerous ways of setting the colors of the scatter points.

    (a) One easy way is to supply a list of colors.

    colors = ['red','red','red','blue','red','blue']
ax.scatter(data[:,0],data[:,1],c=colors,marker="o", picker=True)

    (b) Another option is to supply a list of data and map the data to color using a colormap

    colors = [0,0,0,1,0,1] #red is 0, blue is 1
ax.scatter(data[:,0],data[:,1],c=colors,marker="o", cmap="bwr_r")