Finding x value for y values on a dataset.

Say I have this matrix:

y = [-5 -4 -3 -2 -1 0 1 2 3 4 5;

-6 -5 -4 -3 -2 -1 0 1 2 3 4;

0 1 2 3 4 5 6 7 8 9 10];

And this is my domain:

x = [0 1 2 3 4 5 6 7 8 9 10 ];

and I plot them like so

plot(x, y)

How can I find the x values when my y values cross a value like 3.5?

I would like my output to be

output = [9 10 5]

Thanks!

Answer 1

[the cyclist]

The algorithm you want is not perfectly clear, and I can't see quite how you get the output from your input. But it seems that you want something like this?

y = [-5 -4 -3 -2 -1  0 1 2 3 4  5; 
     -6 -5 -4 -3 -2 -1 0 1 2 3  4;
      0  1  2  3  4  5 6 7 8 9 10];
 
nyrows = size(y,1);

output = zeros(1,nyrows);

for ny = 1:nyrows
    output(ny) = find(y(ny,:)>3.5,1) - 1; % Not sure exactly which element you want
end

disp(output)

     9    10     4

[Alexander Huang]

Exactly what I needed, thank you!