How to make pcolor plot from three vector

Question

Aristo 2017-9-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/355468-how-to-make-pcolor-plot-from-three-vector

评论： Aristo 2018-1-12

采纳的回答： Kelly Kearney

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I have matrix A of size 3X250, where in the value of altitude corresponds to longitude and latitude

A= [latitude, longitude, altitude]

I want to plot pcolor for latitude and longitude with bin/grid size of 5 degree, where in bin should contain mean data of altitude within the 5 degree bin and should reflect in the colorbar. The plot should look somewhat like the following

Thanks for your inputs in advance

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Answer 1

Kelly Kearney 2017-9-6

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/355468-how-to-make-pcolor-plot-from-three-vector#answer_280509

在 MATLAB Online 中打开

You can calculate the bin averages pretty quickly using discretize and accumarray:

Some sample data:

npt = 10000;
A = [rand(npt,1)*180-90 rand(npt,1)*360-180 rand(npt,1)];

5-degree bins:

latbin = -90:5:90;
lonbin = -180:5:180;
nlat = length(latbin);
nlon = length(lonbin);

Use discretize to figure out which latitude and longitude bin each point falls into, then convert the row/column indices into a single array index.

ilat = discretize(A(:,1), latbin);
ilon = discretize(A(:,2), lonbin);
idx = sub2ind([nlat nlon], ilat, ilon);

Use accumarray to average the values assigned to each index, then reshape to a grid:

altg = accumarray(idx, A(:,3), [nlat*nlon 1], @(x) mean(x), NaN);
altg = reshape(altg, nlat, nlon);

Finally, plot:

pcolor(lonbin, latbin, altg);

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Aristo 2018-1-12

I wanted to apply 'shading interp' for the above code, If one of them is Nan, this point is not coloreated since the interpolation is between 4 vertices, what is the other alternative for it

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