Mauro Cavalcanti wrote:
> Dear ALL,
>
> Good morning! Here am I again with the first (and perhaps simpler)
> part of a potentially long question on plotting gridded data using MPL
> (*and* Basemap).
>
> Most examples I have found of plotting gridded data (using either
> MATLAB or MPL) depict highly sophisticated 3D plots that are much more
> than I can need, which turn to be plotting of data onto a geographic
> (therefore, regular and 2D) grid and displaying the plot over a
> Basemap (usually, but not necessarily, using an Equirectangular
> projection) -- so that I can come up with something like the attached
> figure.
>
> To begin with, here are some general questions:
>
> 1) Can a plot like this one (but not necessarily identical) be done
> with MPL/Basemap from gridded data?
>
Mauro: The answer is yes. It looks like a pcolor plot with missing
data over the oceans, so you will probably have to use a masked array
for the data with the ocean values masked.
> 2) For constructing the grid, I have to use the NumPy meshgrid()
> method, as the data are regularly spaced on a geographic grid. For
> example:
>
> import numpy
> import matplotlib.pyplot as plt
>
> coords = numpy.loadtxt('grid.dat')
> lon = coords[:,0]
> lat = coords[:,1]
> dat = coords[:,2]
> X, Y = numpy.meshgrid(lon, lat)
>
> where grid.dat is as follows (very simple dataset, just for
> demonstration purposes):
>
> -61.05 10.4 20
> -79.43 9.15 50
> -70.66 9.53 10
> -63.11 7.91 40
> -63.11 10.55 20
> -81.18 7.51 80
> -56.48 3.1 90
> -60.5 3.93 10
> -81.01 7.66 5
> -67.43 8.93 10
> -65.96 10.31 20
> -78.93 8.38 30
> -72.86 9.83 40
> -68.4 10.61 40
> -72.98 10.61 20
>
> The first two columns correspond to longitude, latitude, and the third
> correspond to the variable to be plotted onto the grid (species
> richness).
>
> The above script reads the data and generates the grid, but then, how
> can I display it on a 2D grid overlaid on a Basemap?
>
Assuming that this is a regular grid (so that using meshgrid makes
sense) you can
using pcolor:
m.pcolormesh(x,y,dat)
using contourf:
m.contourf(x,y,dat,clevs)
using imshow:
m.imshow(dat)
There are examples of all three included with basemap.
HTH,
-Jeff
> Well, as I mentioned above, this is the first part of a longer
> question (but I cannot pursue it first before solving these one
> first).
>
> Thanks in advance for any assistance you can provide.
>
> With best regards,
>
>
>
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--
Jeffrey S. Whitaker Phone : (303)497-6313
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