# How To: Plot a Function of Two Variables with matplotlib

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Join For FreeIn this post we will see how to visualize a function of two variables in two ways. First, we will create an intensity image of the function and, second, we will use the 3D plotting capabilities of matplotlib to create a shaded surface plot. So, let's go with the code:

from numpy import exp,arange from pylab import meshgrid,cm,imshow,contour,clabel,colorbar,axis,title,show # the function that I'm going to plot def z_func(x,y): return (1-(x**2+y**3))*exp(-(x**2+y**2)/2) x = arange(-3.0,3.0,0.1) y = arange(-3.0,3.0,0.1) X,Y = meshgrid(x, y) # grid of point Z = z_func(X, Y) # evaluation of the function on the grid im = imshow(Z,cmap=cm.RdBu) # drawing the function # adding the Contour lines with labels cset = contour(Z,arange(-1,1.5,0.2),linewidths=2,cmap=cm.Set2) clabel(cset,inline=True,fmt='%1.1f',fontsize=10) colorbar(im) # adding the colobar on the right # latex fashion title title('$z=(1-x^2+y^3) e^{-(x^2+y^2)/2}$') show()

The script would have the following output:

And now we are going to use the values stored in X,Y and Z to make a 3D plot using the mplot3d toolkit. Here's the snippet:

from mpl_toolkits.mplot3d import Axes3D from matplotlib import cm from matplotlib.ticker import LinearLocator, FormatStrFormatter import matplotlib.pyplot as plt from numpy import sin,sqrt fig = plt.figure() ax = fig.gca(projection='3d') surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap=cm.RdBu,linewidth=0, antialiased=False) ax.zaxis.set_major_locator(LinearLocator(10)) ax.zaxis.set_major_formatter(FormatStrFormatter('%.02f')) fig.colorbar(surf, shrink=0.5, aspect=5) plt.show()

And this is the result:

*Source: http://glowingpython.blogspot.com/2012/01/how-to-plot-two-variable-functions-with.html*

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