How Can I Color Scatter Markers by Values of a Third Variable in Matplotlib?

Coloring Scatter Markers by Values of a Third Variable

In matplotlib, scatterplots can be used to visualize relationships between data points. To add more depth to these plots, points can be shaded according to a third variable. Below is a straightforward approach for achieving this.

The code snippet below demonstrates how to create a scatterplot where points are shaded according to a third variable:

plt.scatter(w, M, c=p, marker='s')

Here, w and M represent data points, while p signifies the variable used for shading.

To display the plot in grayscale, remove the color specification and utilize a grayscale colormap:

import matplotlib.pyplot as plt

# Generate data...
x = np.random.random(10)
y = np.random.random(10)

# Plot...
plt.scatter(x, y, c=y, s=500)
plt.gray()

plt.show()

This code uses the plt.gray() method to automatically assign grayscale values to the points.

Alternatively, one can specify a specific grayscale colormap through the cmap keyword argument in scatter. The options include 'gray', 'gist_yarg', 'binary', and others. The reversed version of a colormap can be chosen by adding "_r" to its name.

plt.scatter(x, y, c=y, s=500, cmap='gray')

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