Creating a profile of 2D array

Hi everyone.

If I have a 2D matrix (1000,1000) and I want to know for example the index od the point (3.6,100), how can I do this?

If I know theses value I can plot this profile indexing my matrix.

Anyone have other ideia of how can I do it?

For everyone to better understand my problem, here's my code:

And I want to criate profiles of Q along that figure.

if you can help me I appreciate it very much.

wc = 2e8;

einf = 2;

es=linspace(0.1,22,1000);

tau =linspace(7e-12,100e-12,1000);

deltae = es-einf;


for i = 1:1000;
    for j = 1:1000;
        Q(i,j)= ( einf + ( deltae(i) )/( 1 + (wc^2) * (tau(j).^2 ) ))/((deltae(i) * (tau(j)) *wc )/( 1 + (wc^2) * (tau(j).^2)));
        

     end
end    

contour(deltae,tau,Q,[10;20;50;70;100;200;300;400;500;600;700;800;900;1000;2000]);

[Ameer Hamza]

Each element in the 2D matrix is a single element. What does (3.6,100) represent?

[Bruno Barauna]

Represents a cartesian point. I want to get the index matrix of this point.

Answer 1

[KSSV]

I hope you have X, Y, Z matrices of size specified. And you want to know the value at given point (x,y). IN that case you need to use interp2.

iwant = interp2(X,Y,Z,3.6,100) ;

[Bruno Barauna]

In this case the cartesian point is, for example, (3.6, 100). I had written wrong. I'm sorry.

But the question is, how can I get the matrix index of these cartesian point ?

Thank you.