Matrix Interpolation coordinates interp1

Hey guys, I'm trying to do something which should be simple but I just can't seem to write it. I have a matrix FX, and two vectors of coordinates, x&y, and these coordinates are changing in an iterative loop.

After each iteration, I need to find the value of FX at the new coordinates (FX(x,y)) but the coordinates aren't integers, so I need to do some sort of interpolation to find the closest F(xi, yi) that I can. I was thinking it would just be,

fex = interp1([round(x),round(y)],FX,[x,y], 'linear')

But that complains about not being monotonic (they're not meant to be). Any ideas on how to approach this one?

Thanks

Answer 1

[Matt J]

Use griddedInterpolant,

     f=griddedInterpolant(FX);  %Do this prior to loop

     for i=1:N

       %generate x and y

        fex=f(x,y);

     end

[James]

works great, thanks :)