How do I make a heat/color map from individual data points?

Question

Hunter Adams 2022-2-21

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https://ww2.mathworks.cn/matlabcentral/answers/1655240-how-do-i-make-a-heat-color-map-from-individual-data-points

编辑： AndresVar 2022-2-23

Howdy,

I'm relatively new to Matlab and would like to create a heatmap of nitrous oxide concentration with contours over a region kind of like this with a colorbar:

I have latitude, longitude, and nitrous oxide concentration data for specific points.

I know you can use the heatmap function and data from a matrix to make a plot like the one above but I do not know how to fill in the gaps of my individual data points across the region. Any help or methodology is appreciated and let me know if there's anymore information I can provide that might help!

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Answer 1

AndresVar 2022-2-21

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You can interpolate between the points using gridded data interpolation: Interpolate 2-D or 3-D scattered data - MATLAB griddata (mathworks.com)

Then with the interpolated matrix you can display in a few ways:

You can use pcolor to create a pseudocolor concentration map with interpolation: Pseudocolor plot - MATLAB pcolor (mathworks.com)
Also imagesc is practical: Display image with scaled colors - MATLAB imagesc (mathworks.com)
There is also countourf if you want to show contour lines Filled 2-D contour plot - MATLAB contourf (mathworks.com)

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Hunter Adams 2022-2-22

在 MATLAB Online 中打开

dat = xlsread('Book2.xlsx');
stations = dat(:,1);
niskin = dat(:,2);
depth = dat(:,3);
lat = dat(:,4);
lon = dat(:,5);
sal = dat(:,6);
oxy = dat(:,7);
n2o = dat(:,8);
[xq, yq] = meshgrid(-89.5:.25:-88.5, 28.7:.25,30);
vq = griddata(lat,lon,n2o,xq,yq);
vq = griddata(lat,lon,n2o,xq,yq);
mesh(xq,yq,vq)
hold on
plot3(lat,lon,n2o,'-bo')
%pcolor(vq)
%contourf(vq)

pcolor has an error creating/updating surface and contourf creates a blank figure. Do you know what I'm missing? The 3D plot works fine. Just need to make it 2D and give color to the n2o concentration.

AndresVar 2022-2-23

编辑：AndresVar 2022-2-23

在 MATLAB Online 中打开

your meshgrid is not right so it returns empty xq and yq

[xq, yq] = meshgrid(-89.5:.25:-88.5, 28.7:.25,30) % comma is wrong
xq =

     []


yq =

     []
[xq, yq] = meshgrid(-89.5:.25:-88.5, 28.7:.25:30)
xq = 6×5
  -89.5000  -89.2500  -89.0000  -88.7500  -88.5000
  -89.5000  -89.2500  -89.0000  -88.7500  -88.5000
  -89.5000  -89.2500  -89.0000  -88.7500  -88.5000
  -89.5000  -89.2500  -89.0000  -88.7500  -88.5000
  -89.5000  -89.2500  -89.0000  -88.7500  -88.5000
  -89.5000  -89.2500  -89.0000  -88.7500  -88.5000
yq = 6×5
   28.7000   28.7000   28.7000   28.7000   28.7000
   28.9500   28.9500   28.9500   28.9500   28.9500
   29.2000   29.2000   29.2000   29.2000   29.2000
   29.4500   29.4500   29.4500   29.4500   29.4500
   29.7000   29.7000   29.7000   29.7000   29.7000
   29.9500   29.9500   29.9500   29.9500   29.9500

Btw when you plot you can use

% figure;
% pc1 = pcolor(xq,yq,vq)
% pc1.EdgeColor = 'none';
% pc1.FaceColor = 'interp';

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How do I make a heat/color map from individual data points?

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