MATLAB: How to mask data points outside a border using geoshow

contourcmapdisplaytypefilterinpolygonmappingmarkingsurface

Hello,
I am using the presented code of this thread to mask the data points outside the border so that only data points within are displayed. Works fine so far. However, I want to use the DisplayType surface. Thus I am using geoshow to plot the data. Unfortunately it does not fill the whole map within the borders as a buffer is left.
Any ideas on this?
Here is an example:
S = shaperead('landareas', 'UseGeoCoords', true,...
  'Selector',{@(name) strcmp(name,'Australia'), 'Name'});
x = linspace(min(S.Lon), max(S.Lon), 100);
y = linspace(min(S.Lat), max(S.Lat), 100);
[x,y] = meshgrid(x,y);
a = 1;
b = 9;
z = a + (b-a).*rand(100,100);
isin = inpolygon(x,y,S.Lon,S.Lat);
z2 = z;
z2(~isin) = NaN;
lnlim = [min(S.Lon) max(S.Lon)];
ltlim = [min(S.Lat) max(S.Lat)];
lt = linspace(ltlim(1), ltlim(2), 3);
ln = linspace(lnlim(1), lnlim(2), 3);
for ii = 1:2
    ltbox{ii} = lt([1 2 2 1 1]'+(ii-1));
    lnbox{ii} = ln([1 1 2 2 1]'+(ii-1));
end
[lnmask, ltmask] = deal(cell(2));
for ii = 1:2
    for jj = 1:2
        [lnmask{ii,jj}, ltmask{ii,jj}] = polybool('-', ...
        lnbox{ii}, ltbox{jj}, S.Lon, S.Lat);
    end
end
ltboxall = ltlim([1 2 2 1 1]);
lnboxall = lnlim([1 1 2 2 1]);
[lnmaskall, ltmaskall] = polybool('-', lnboxall, ltboxall, S.Lon, S.Lat);
figure('color','w');
worldmap('Australia');
geoshow(y, x, z2, 'DisplayType','surface')
contourcmap('jet',round(min(z2(:)),2,'significant'):1:round(max(z2(:)),...
    2,'significant'),'colorbar','on','location','vertical')
for ii = 1:4
    patchm(ltmask{ii},  lnmask{ii}, 'w', 'edgecolor', 'none');
end
plotm(ltmaskall, lnmaskall, 'k');

Best Answer

You seem to have combined both of my suggested methods into one in this example. Are you trying to do the mask-with-NaNs option (which is easier, but may leave you with some jagged edges near the country border)? Or the patch overlay?
Either way, I think the "not filling" issue you're seeing is an artifact of how worldmap defines Australia versus how the shapefile does. The former includes a wider longitude range, probably accounting for a small island or two off the east coast somewhere (my Australian geography leaves something to be desired). If instead you call worldmap with your data limits, you should see better results:
worldmap(ltlim, lnlim);
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