solving two-variable matrix function

Hi,

so assume I have a function like this:

f = [x(1) + x(2) ; x(2) * x(1)]

and my x = [2; -2]

how can I solve it? feval doesnt work for some reason ("Dimensions of arrays being concatenated are not consistent)

Answer 1

[Jiri Hajek]

Hi this can be done using inline function very efficiently like this:

fh=@(x,y)[x+y,x*y];
fh(2,-2)

ans = 1×2

0 -4

[Dmitry Solomatin]

Thanks it now works, but for some reason this gives me a 1x3 matrix and it should only 1x2?

fh = @ (x,y) [2*x- 400*x*(-x^2+y) -2, 200 * (y-x^2)];
fh(2,-2) 

[Jiri Hajek]

This is because Matlab interprets space within brackets as a separator of vector elements, same as a comma. You can eithertake away all the spaces or put your expressions into parentheses. That way, you can forget about the meaning of spaces:

fh = @ (x,y) [(2*x- 400*x*(-x^2+y) -2), (200 * (y-x^2))]

fh = function_handle with value:
    @(x,y)[(2*x-400*x*(-x^2+y)-2),(200*(y-x^2))]

fh(2,-2) 

ans = 1×2

4802 -1200