find coordinate(-s) on a plot
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![coord.PNG](https://www.mathworks.com/matlabcentral/answers/uploaded_files/237302/coord.png)
I have the plot you see above (plotted from data of two vectros X and Y). And I would like to find the coordinates x where y =10. Usually if the y value appears only one time, then I can use the interp1 function.
But what about when this y value belongs to 2 or more x coordinates?
2 Comments
dpb
on 7 Sep 2019
Look for crossing the threshold -- hint: what happens in sign(diff(y)-threshold) when the crossing is rising or falling?
Answers (1)
Nishant Gupta
on 10 Sep 2019
Hi Argy,
You can use logical indexing to find the x-ordinates corresponding to y = 10 as follows:
x = [1 2 3 4 5]; % x vector
y = [15 10 25 10 5]; % y vector
plot(x,y);
hold on;
yline(10); % plot horizontal line at y = 10
idx = find(y==10);
for i = 1:numel(idx)
xline(x(idx(i))); % to get vertical line at all x-ordinates corresponding to y = 10
end
hold off;
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