Filling a polygon using an index and colormap

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

Answer 1

[Rob Comer]

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')

[Walter Roberson]

Giuliano Langella comments,

"very useful to map continuous numerical attribute!"

[li linjiang]

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')