How to fill polygons based on attribute values?

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Keegan Carvalho 2022-6-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1746185-how-to-fill-polygons-based-on-attribute-values

编辑： Keegan Carvalho 2022-6-24

采纳的回答： KSSV

Expot.zip

在 MATLAB Online 中打开

I have used the following code to load and plot the shapefile "Expot.shp" (attaced zip file). I wanted to plot the "Corr" attribute, but for some reason the colour does not match the values. (Also, the "Corr" values with zeros are basically not calculated - can treat them as NaNs)

landAreas = readgeotable("landareas.shp");               %from "geoshow" matlab documentation
row = landAreas.Name == "North and South America";
landAreasSubset = landAreas(row,:);
corr = shaperead("Expot.shp")
cmap = jet(256);
colorRange = makesymbolspec("Polygon", ...
{'Corr',[-0.02 0.05],'FaceColor',cmap});                  %Use makesymbolspec to specify polygon colors
mapshow(corr,"SymbolSpec",colorRange)
colormap(cmap)
caxis([-0.02 0.05])
colorbar
hold on
geoshow(landAreasSubset)

The result map is attached below

The legend shows the "Corr" values but the map does not. I'd like to know where I seem to be going wrong; I think there's a line of code missing or needs to be changed.

I'd be grateful for assistance on this. Thank You

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采纳的回答

KSSV 2022-6-23

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1746185-how-to-fill-polygons-based-on-attribute-values#answer_991535

编辑：KSSV 2022-6-23

在 MATLAB Online 中打开

How about this?

shpFile = 'Expot.shp' ; 
S = shaperead(shpFile) ;
N = length(S) ; 
cmap = jet(N) ; 
figure
hold on
for i = 1:N
    x = S(i).X ; y = S(i).Y ; 
    x(isnan(x))=[] ; 
    y(isnan(y))=[] ;     
    patch(x,y,cmap(i,:)) ;
end
colorbar
colormap(cmap)

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KSSV 2022-6-23

This is the correct mapping of corr right?

Keegan Carvalho 2022-6-24

编辑：Keegan Carvalho 2022-6-24

Not quite. The regions with values "0", I prefer not having a colour for them, becasue they are essentially "NaN" values. Is there a way to code to show no colour for the polygons with "0" values?

If the regions with "0" show no color, then I can determine if it is correct. Because most of the polygons with "0" show different colours in the above map

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