i have number of points that have (x,y) .then i define a line and i want to realize which points are under the line?

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Mili Kian on 18 Apr 2020
Commented: Mili Kian on 24 Apr 2020
i have number of points that have (x,y) .then i define a line and i want to realize which points are under the line?
i write this :
....
r=[0 10 15 20 30];
t=[10 10 15 10 10];
f= line(r,t)
axis([0,30,0,20]);
d=(eldof(:,10))& (eldof(:,11)) <= f
then all of points are zero
why??

Image Analyst on 18 Apr 2020
You need to call polyfit:
coefficients = polyfit(r, t, 1);
or you can call fitPolynomialRansac if you want the line to go exactly through the points on the bottom of your plot.
Then you have to get some x values and get a digital vector of line values. You can use your r locations, or you can use more or less than that. Then see which values are less than the y value of the line. For the same r points
yLine = polyval(coefficients, r);
belowLine = t < yLine; % A logical index vector.
Image Analyst on 20 Apr 2020
Those points are just a grid: I'm not sure what to do either. Can you draw the line on there that you want to detect if some point is below that line, and repost your picture with the line indicated?

Mili Kian on 21 Apr 2020 i want to see the effect of topoghraphy
Mili Kian on 24 Apr 2020
thank you
and sory for delay