How can I put Alaska map as a background behind my contour plots?

Hi all,

Using the following code I could develope countour maps showing freezing depth across the Alaska states. How can I plot these contour maps in a way that the background would be the Alaska map? The x and y axis are longitude and latitude respectively.

clear
close all
clc
load('POFDE.mat');
data = cell2mat(POFDE);
[lat,lon] = meshgrid(unique(data(:,1)),unique(data(:,2)));
for i = 1:(size(data, 2)-2)
    figure
    I = scatteredInterpolant(data(:,[1 2]), data(:,i+2));
    contourf(lon,lat,min(1,max(0,I(lat,lon))),'ShowText','on')
    colorbar
    title(['The probability of frost depth exceedance of \Omega_{\delta} = ' num2str(i) ' feet'])
    exportgraphics(gca, sprintf('FrostPlot_%d_feet.png', i))
end

[Ashfaq Ahmed]

You will find the map of Alaska and easily plot this using this toolbox -

Arctic Mapping Toolbox

Answer 1

[the cyclist]

If you have the Mapping Toolbox, you can use the usamap function to make an Alaska map, and superimpose your other data on it.

[Behrooz Daneshian]

Thank you for your reply. However, when I use usamap function and hold on together, contours will not be displayed!

clear
close all
clc
load('POFDE.mat');
data = cell2mat(POFDE);
[lat,lon] = meshgrid(unique(data(:,1)),unique(data(:,2)));
for i = 1:(size(data, 2)-2)
    figure
    usamap("Alaska")
    states = readgeotable("usastatehi.shp");
    row = states.Name == "Alaska";
    alaska = states(row,:);
    geoshow(alaska,"FaceColor",[0.3 1.0, 0.675])
    textm(alaska.LabelLat,alaska.LabelLon,alaska.Name, ...
        "HorizontalAlignment","center")
    hold on;
    I = scatteredInterpolant(data(:,[1 2]), data(:,i+2));
    contourm(lon,lat,min(1,max(0,I(lat,lon))),'ShowText','on')
    colorbar
    title(['The probability of frost depth exceedance of \Omega_{\delta} = ' num2str(i) ' feet'])
    exportgraphics(gca, sprintf('FrostPlot_%d_feet.png', i))
    hold off
end

Answer 2

[Star Strider]

You have ‘lat’ and ‘lon’ reversed in the first two arguments to the contourm call.

Reversing them —

% clear
% close all
% clc
% load('POFDE.mat');
load(websave('POFDE','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1299285/POFDE.mat'))
data = cell2mat(POFDE);
[lat,lon] = meshgrid(unique(data(:,1)),unique(data(:,2)));
for i = 1:(size(data, 2)-2)
    figure
    usamap("Alaska")
    states = readgeotable("usastatehi.shp");
    row = states.Name == "Alaska";
    alaska = states(row,:);
    geoshow(alaska,"FaceColor",[0.3 1.0, 0.675])
    textm(alaska.LabelLat,alaska.LabelLon,alaska.Name, ...
        "HorizontalAlignment","center")
    hold on;
    I = scatteredInterpolant(data(:,[1 2]), data(:,i+2));
    contourm(lat,lon,I(lat,lon), 'LineWidth',2,'ShowText','on')
    colormap(turbo)
    colorbar
    title(['The probability of frost depth exceedance of \Omega_{\delta} = ' num2str(i) ' feet'])
%     exportgraphics(gca, sprintf('FrostPlot_%d_feet.png', i))
    hold off
end

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

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