I want to color code US states by specific metrics. What is the easiest way to do this?

I know how to create a conus map

ax = usamap('conus');
%ax = worldmap('USA');
load coastlines
geoshow(ax, coastlat, coastlon,...
    'DisplayType', 'polygon', 'FaceColor', [.45 .60 .30])
states = shaperead('usastatelo', 'UseGeoCoords', true);
faceColors = makesymbolspec('Polygon',...
    {'INDEX', [1 numel(states)], 'FaceColor', ...
    polcmap(numel(states))}); % NOTE - colors are random
geoshow(ax, states, 'DisplayType', 'polygon', ...
    'SymbolSpec', faceColors)

But how do I highlight states by specific metrics such as number of occurrances by specific category?

Answer 1

[Voss]

Here's how you can make a map colored by log10 of Population Density (2000), which is the variable color_value below. You can change that metric to whatever you want, and the rest of the code is the same.

ax = usamap('conus');
load coastlines
geoshow(ax, coastlat, coastlon,...
    'DisplayType', 'polygon', 'FaceColor', [.45 .60 .30])

states = shaperead('usastatelo', 'UseGeoCoords', true)

states = 51×1 struct array with fields:
    Geometry
    BoundingBox
    Lon
    Lat
    Name
    LabelLat
    LabelLon
    PopDens2000

% - color the states by PopDens2000, since we have that data here in the 
%   "states" struct array
% - throw out DC since its population density is much higher (~9000) than 
%   all the actual states (~1.1 to ~1100)
% - throw out Alaska and Hawaii since they won't show up on the map
%   (which shows the continental US) - in particular, Alaska's
%   population density is the lowest of all the states, and you don't want 
%   it determining the colors of the other states if Alaska is not even 
%   shown on the map
states(ismember({states.Name},{'District of Columbia' 'Alaska' 'Hawaii'})) = [];

% use a log color scale:
color_value = log10([states.PopDens2000]);

% pick a colormap to use:
color_map = parula();

% get the min and max color_value:
color_limits = [min(color_value) max(color_value)];

% convert color_value into an index in color_map:
% - minimum color_value goes to 1
% - maximum color_value goes to size(color_map,1)
color_idx = round((color_value-color_limits(1))/(color_limits(2)-color_limits(1))*(size(color_map,1)-1))+1;

% index into color_map using color_idx to 
% get the colors to use for each state
faceColors = makesymbolspec('Polygon',{ ...
    'INDEX',[1 numel(states)], ...
    'FaceColor',color_map(color_idx,:)});

% show the states
geoshow(ax,states,'DisplayType','polygon','SymbolSpec',faceColors);

% make a colorbar
colormap(color_map);
colorbar('YAxisLocation','left');
clim(10.^color_limits);

[Voss]

("Answer" from @Thomas Burbey moved here:)

Thank you for your prompt and awesome answer. Greatly appreciated.

[Voss]

You're welcome!