You could use colorbar‘s format parameter: import matplotlib.pyplot as plt import numpy as np import matplotlib.ticker as ticker img = np.random.randn(300,300) myplot = plt.imshow(img) def fmt(x, pos): a, b = ‘{:.2e}’.format(x).split(‘e’) b = int(b) return r’${} \times 10^{{{}}}$’.format(a, b) plt.colorbar(myplot, format=ticker.FuncFormatter(fmt)) plt.show()
I’m not quite sure if this qualifies within “not knowing the inner structure of the colormap”, but perhaps something like this would work to add a linear alpha to an existing colormap? import numpy as np import matplotlib.pylab as pl from matplotlib.colors import ListedColormap # Random data data1 = np.random.random((4,4)) # Choose colormap cmap = … Read more
Using vmin and vmax forces the range for the colors. Here’s an example: import matplotlib as m import matplotlib.pyplot as plt import numpy as np cdict = { ‘red’ : ( (0.0, 0.25, .25), (0.02, .59, .59), (1., 1., 1.)), ‘green’: ( (0.0, 0.0, 0.0), (0.02, .45, .45), (1., .97, .97)), ‘blue’ : ( (0.0, … Read more
You can create some dummy image and then hide it’s axe. Draw your colorbar in a customize Axes. import pylab as pl import numpy as np a = np.array([[0,1]]) pl.figure(figsize=(9, 1.5)) img = pl.imshow(a, cmap=”Blues”) pl.gca().set_visible(False) cax = pl.axes([0.1, 0.2, 0.8, 0.6]) pl.colorbar(orientation=”h”, cax=cax) pl.savefig(“colorbar.pdf”) the result:
Sometimes it can be useful to retrieve a colorbar even if it was not held in a variable. In this case, it is possible to retrieve the colorbar from the plot with: # Create an example image and colourbar img = np.arange(20).reshape(5,4) plt.imshow(img) plt.colorbar() # Get the current axis ax = plt.gca() # Get the … Read more
If I understand correctly what you want, I think this should do it: import numpy as np import matplotlib.pyplot as plt xi = np.array([0., 0.5, 1.0]) yi = np.array([0., 0.5, 1.0]) zi = np.array([[0., 1.0, 2.0], [0., 1.0, 2.0], [-0.1, 1.0, 2.0]]) v = np.linspace(-.1, 2.0, 15, endpoint=True) plt.contour(xi, yi, zi, v, linewidths=0.5, colors=”k”) plt.contourf(xi, … Read more
Not to steal @ianilis’s answer, but I wanted to add an example… There are multiple ways, but the simplest is just to specify the vmin and vmax kwargs to imshow. Alternately, you can make a matplotlib.cm.Colormap instance and specify it, but that’s more complicated than necessary for simple cases. Here’s a quick example with a … Read more
cb.set_label(“Foo”, labelpad=-1) Negative labelpad values will move closer to the bar, positive away.
You could use colorbar‘s format parameter: import matplotlib.pyplot as plt import numpy as np import matplotlib.ticker as ticker img = np.random.randn(300,300) myplot = plt.imshow(img) def fmt(x, pos): a, b = ‘{:.2e}’.format(x).split(‘e’) b = int(b) return r’${} \times 10^{{{}}}$’.format(a, b) plt.colorbar(myplot, format=ticker.FuncFormatter(fmt)) plt.show()
I think the problem is that with del you cancel the variable, but not the referenced object colorbar. If you want the colorbar to be removed from plot and disappear, you have to use the method remove of the colorbar instance and to do this you need to have the colorbar in a variable, for … Read more