Plotting color coded markers in matplotlib-basemap

Question

I have the following variables, that I want to plot on a map: Lons, a list of longitudes, Lats, a list of latitudes and Vals, a list of values for each location.

To plot the locations, I do a simple

x,y=Mymap(Lons,Lats)
Mymap.scatter(x,y,marker='o',color='red')

Q: how do i best turn my Vals into a list of colors (heatmap) to be passed intoscatter, so that every x,y pair gets its values matching color?

The basemap docs are rather lacking, and none of the examples fits my purposes.

I could probably loop through my whole Lats, Lons and Vals but given how slow basemap is, I'd rather avoid that. I already have to draw about 800 maps, and increasing that to about 1 Million will probably take years.

Answer 1

The basemap scatter documentation simply refers to the pyplot.scatter documentation, where you can find the parameter c (emphasis mine):

c : color or sequence of color, optional, default

c can be a single color format string, or a sequence of color specifications of length N, or a sequence of N numbers to be mapped to colors using the cmap and norm specified via kwargs (see below). Note that c should not be a single numeric RGB or RGBA sequence because that is indistinguishable from an array of values to be colormapped. c can be a 2-D array in which the rows are RGB or RGBA, however.

So if you simply pass vals to c, matplotlib should convert the values to colors on the standard colormap or a chosen colormap. To show which color is mapped to what value you can use the colorbar.

Example code:

import matplotlib.pyplot as plt

lons = range(50)
lats = range(25, 75)
vals = range(50,100)

plt.scatter(lons, lats, c=vals, cmap='afmhot')
plt.colorbar()
plt.show()