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Filling a polygon using an index and colormap

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Kenneth Morley
Kenneth Morley on 27 Jan 2014
Commented: li linjiang on 6 May 2020
I am attempting to fill in the polygons of counties based on data collected. I have attached the array I am working with. It has 61 counties. I would like to fill these counties based on the values in counties.risk. How can I do this? I have been using geoshow to show the counties up until now. Thanks so much for your help!
Kenny

Accepted Answer

Rob Comer
Rob Comer on 29 Jan 2014
The key to making many thematic maps is to use the makesymbolspec function in combination with geoshow or mapshow . In this case, because polygons are being color-coded, it's more specifically a "choropleth map."
load ToUpload
figure('Color','white')
worldmap([20 35],[-100 -78])
colormap(summer(512))
riskSymbolSpec = makesymbolspec('Polygon', ...
{'risk',[0 40],'FaceColor',colormap});
geoshow(counties,'SymbolSpec',riskSymbolSpec)
colorbar
caxis([0 40])
set(get(colorbar,'YLabel'),'String','risk')
  2 Comments
li linjiang
li linjiang on 6 May 2020
When i test with my data, it is not correct. Some Polygons can not be filled. here is my code:
clear;
load mydata
figure('Color','white')
%worldmap([20 35],[-100 -78])
colormap(summer(512))
riskSymbolSpec = makesymbolspec('Polygon', ...
{'risk',[0 40],'FaceColor',colormap,'EdgeColor','g'});
geoshow(counties,'SymbolSpec',riskSymbolSpec)
colorbar
hold on
xlim([121.5 122]);
ylim([31 31.5]);
caxis([0 40])
set(get(colorbar,'YLabel'),'String','risk')

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