CODEWITHSUNDEEP
matlabplotcontour
Pep
Pep

Reputation: 147

summation of level values from contour plot

I'm trying to compute the sum of the level (z axis) values inside a contour: enter image description here

I've managed to obtain the lines (or edges) of the contour, so I have the limits of each line:

enter image description here

What I want is to sum all the levels in the z axis of the contour that are inside the outer blue line in the second plot, to compare it with the sum of the values of outside the blue line. Is there any way to do this? The code I have so far is:

   C = contourc(f, t, abs(tfr));

%extracts info from contour    
    sz = size(C,2);     % Size of the contour matrix c
    ii = 1;             % Index to keep track of current location
    jj = 1;             % Counter to keep track of # of contour lines

    while ii < sz       % While we haven't exhausted the array
        n = C(2,ii);    % How many points in this contour?
        s(jj).v = C(1,ii);        % Value of the contour
        s(jj).x = C(1,ii+1:ii+n); % X coordinates
        s(jj).y = C(2,ii+1:ii+n); % Y coordinates
        ii = ii + n + 1;          % Skip ahead to next contour line
        jj = jj + 1;              % Increment number of contours
    end

Upvotes: 2

Views: 542

Answers (1)

EdR
EdR

Reputation: 533

So after you run the code in the question you have the coordinates of each contour in the array S. Assuming you have variables f and t of the form f = 94:0.1:101 and t = 0:1000 or similar, and the that value you want to sum are abs(tfr) you should be able to use

[fg, tg] = meshgrid(f,t)
is_inside = inpolygon(fg,tg, S(1).x, S(1).y)
integral = sum(abs(tfr(is_inside))

And similarly for other entries in S. See help for inpolygon for more examples. You can use ~is_inside for the points outside the curve

Upvotes: 2

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