Obtaining width of section along a line in contour plot

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Saeid 2017-8-11

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https://ww2.mathworks.cn/matlabcentral/answers/352407-obtaining-width-of-section-along-a-line-in-contour-plot

评论： KSSV 2017-8-11

I use ginput to select a hanful of points on a contour plot, created from xyz data. Now I want to create a vector that e.g. starts at the first point selected and ends at the second point and covers all the points on the route. It would be easy if the selection were always a diagonal matrix but in non-diagonal cases the line usually cuts through two adjacent elements of a row (or column). As stated above I can click on two points of a contour plot to obtain the indices using ginput and the corresponding z values. What I need now is the the maximum z value occurring along the red line and the width of the area under the selected line (red line in picture below).

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Answer 1

KSSV 2017-8-11

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https://ww2.mathworks.cn/matlabcentral/answers/352407-obtaining-width-of-section-along-a-line-in-contour-plot#answer_277673

As you have (x,y) of the red line in hand, use interp2 to get the corresponding z values....to get area use trapz.

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Saeid 2017-8-11

Thanks KSSV, but this was not what I exactly wanted. I don't need an approximation (or interpolation) of what lies under the red line, but the exact existing values of the array that is the source of my plot.

KSSV 2017-8-11

If your point lie's exactly on the given point..you will get what you want...if it is deviated, it will be interpolated....still..if you are particular....you can use knnsearch to get nearest neighbour and extract that pixel.

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