Matplotlib Tutorial FAQ#

Here is a compilation of questions and issues that arose during the Matplotlib session of the Python Tutorial Seminar Series.

Q. Are all the colormaps perceptually ordered?

A. They are not all perceptually ordered. Any color map you can think of exists or can be made. The Matplotlib Documentation has a good guide for choosing colormaps.

Q. How do you set the x-axis boundary to remove the padding left and right of where the data begins/ends?

A. You would use ax.set_xlim and provide the minimum and maximum x-values as input. You can infer these from your x data with the full command ax.set_xlim([min(x), max(x)]).

Q. How do you create a .png from a notebook?

A. You can save a figure by running plt.savefig(‘filename.png’) in the cell you plotted the figure. The file type is inferred from the filename. png, pdf, ps, eps, jpg, and svg are all supported image formats on most backends.

Q. How can we set resolution (dpi) when saving plots?

A. dpi is a keyword argument to savefig. So you can call plt.savefig(FIGURENAME.EXT, dpi=FLOAT) where you specify your desired dots per inch as a float.

Q. How can I add a shared colorbar for the subplots?

A. There are many of examples of how to do this in the GeoCAT-examples documentation. Here is an example that does so while plotting EOFs of the Sea Level Pressure over the North Atlantic. The Matplotlib documentation also has great instructions on how to manipulate colorbars.