I need to get counterlines outside the U.S. removed (Ocean/Canada/Mexico)! Se script below.

I am quite new in using map functions.

This is my simple start script:

clear all
close all
figure
ax = usamap({'CA','NY'});
LATLIM=[24 50]
LONLIM=[-125 -67]
usamap(LATLIM, LONLIM)
set(ax, 'Visible', 'off')
latlim = getm(ax, 'MapLatLimit');
lonlim = getm(ax, 'MapLonLimit');
states = shaperead('usastatehi',...
        'UseGeoCoords', true, 'BoundingBox', [lonlim', latlim']);
 geoshow(ax, states, 'FaceColor', [0.5 0.5 1])
latitude=linspace(min(LATLIM), max(LATLIM));
longitude=linspace(min(LONLIM), max(LONLIM));
n=1;
for i=1:100
    for j=1:100
        lat=latitude(i);
        lin=longitude(j);
        xlat(n)=lat;
        ylon(n)=lin;
     ozone(n)=exp(-((lat-30)^2/9000+(lin-(-100))^2/10000)); %test function
     n=n+1;
    end
end
% Create a grid of latitude and longitude
[LatGrid, LonGrid] = meshgrid(linspace(min(LATLIM), max(LATLIM)), ...
                        linspace(min(LONLIM), max(LONLIM)));
% Use griddata to compute ozone for each grid point
OzoneGrid = griddata(xlat, ylon, ozone, LatGrid, LonGrid);
% Call contourm
contourm(LatGrid, LonGrid, OzoneGrid);

Answer 1

[darova]

Use handler options

% Call contourm
[~,h] = contourm(LatGrid, LonGrid, OzoneGrid);
h1 = get(h,'children');             % for older version
X = get(h1,'xdata');
Y = get(h1,'ydata');

[Carl-Eric Hagentoft]

Hi

I do not follow you! I guess this will give the data points for the contour lines, but

I want to take away the part of the contour lines that is outside the US -country. So how do I continue?

[darova]

Can you show what you don't want to see?

[Carl-Eric Hagentoft]

The curves in the ocean - cirves outside the US.

[darova]

Do you have this program?

[Carl-Eric Hagentoft]

Yes. Of course I can remove the lines in the pictures but I want to do it using Matlab code. I will generate many pictures at several occations.

Maybe there is a way to identify the coordinates of the curve with the borders of the US and remove these points?

[darova]

I just dont understand which part you want to remove

[Carl-Eric Hagentoft]

I want to show the counterlines that is over the ocean. These are of no interest for the user of the pictures. People should be able to read number through the counterlines where they live.

[darova]

I don't how to remove those lines directly on the figure. But you can remove it from the image

clc
fcolor = [0.5 0.5 1];                       % color of states
print('-dpng','-r100','picture1')           % save with resolution
I = imread('picture1.png');                 % read image
[m,n,~] = size(I);
for i = 1:m
    for j = 1:n-1
        if sum(I(i,j,:)) > 255*3-10         % if pixels is white [255 255 255]
            pix = double( I(i,j+1,:) );     % get next pixel
            cond1 = sum(abs(pix(:) - 255*fcolor(:))) < 10;
            cond2 = sum(abs(pix(:) - [0;0;0])) < 10;
            if ~(cond1 || cond2)            % if not facecolor or black
                I(i,j+1,:) = 255;           % remove contour (white color)
            end
        end
    end
end
imshow(I)
imwrite(I,'picture2.png')

[Carl-Eric Hagentoft]

Well it is away to get around it!

Thanks!

[darova]