importmatplotlib.pyplotaspltimportnumpyasnpfromnumpyimportmafrommatplotlibimporttickerN=100x=np.linspace(-3.0,3.0,N)y=np.linspace(-2.0,2.0,N)X,Y=np.meshgrid(x,y)# A low hump with a spike coming out.# Needs to have z/colour axis on a log scale, so we see both hump and spike.# A linear scale only shows the spike.Z1=np.exp(-X**2-Y**2)Z2=np.exp(-(X*10)**2-(Y*10)**2)z=Z1+50*Z2# Put in some negative values (lower left corner) to cause trouble with logs:z[:5,:5]=-1# The following is not strictly essential, but it will eliminate# a warning.  Comment it out to see the warning.z=ma.masked_where(z<=0,z)# Automatic selection of levels works; setting the# log locator tells contourf to use a log scale:fig,ax=plt.subplots()cs=ax.contourf(X,Y,z,locator=ticker.LogLocator(),cmap="PuBu_r")# Alternatively, you can manually set the levels# and the norm:# lev_exp = np.arange(np.floor(np.log10(z.min())-1),#                    np.ceil(np.log10(z.max())+1))# levs = np.power(10, lev_exp)# cs = ax.contourf(X, Y, z, levs, norm=colors.LogNorm())cbar=fig.colorbar(cs)plt.show()

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