pythonmatplotlibscatter-plot

Matplotlib: Scatter Plot to Foreground on top of a Contour Plot


Does anyone know a way to bring a scatter plot to the foreground in matplotlib? I have to display the scatter plotting on top of the contour, but by default it is plotted underneath...


Solution

  • You can manually choose in which order the different plots are to be displayed with the zorder parameter of e.g. the scatter method.

    To demonstrate, see the code below, where the scatter plot in the left subplot has zorder=1 and in the right subplot it has zorder=-1. The object with the highest zorder is placed on top. This means that the scatter will be placed on top of the contour in the first subplot, while it is placed underneath in the second subplot.

    import numpy as np
    import matplotlib.cm as cm
    import matplotlib.mlab as mlab
    import matplotlib.pyplot as plt
    
    delta = 0.025
    x = np.arange(-3.0, 3.0, delta)
    y = np.arange(-2.0, 2.0, delta)
    X, Y = np.meshgrid(x, y)
    Z1 = mlab.bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
    Z2 = mlab.bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
    Z = 10.0 * (Z2 - Z1)
    
    norm = cm.colors.Normalize(vmax=abs(Z).max(), vmin=-abs(Z).max())
    cmap = cm.PRGn
    
    levels = np.arange(-2.0, 1.601, 0.4)
    
    fig, axes = plt.subplots(1,2, sharey=True)
    
    for ax, zord in zip(axes, [1, -1]):
        ax.contourf(X, Y, Z, levels,
                    cmap=cm.get_cmap(cmap, len(levels)-1),
                    norm=norm)
        ax.autoscale(False) # To avoid that the scatter changes limits
        ax.scatter(np.random.uniform(-3,3,10),
                   np.random.uniform(-2,2,10),
                   zorder=zord)
        ax.set_title('Scatter with zorder={0}'.format(zord))
    

    enter image description here