MATLAB: Find value of a constant given a value of z(x,y)

Question

I have the following simplified function:

constant = 5;
z = @(x,y) x + y + constant;

If I want z(4,4) to equal '0', how can I find what value the 'constant' has to be to get me that? I know that I can do a simple arithmetic in the equation above, but what if it's a more complex, multivariate function where it gets really difficult to solve for a variable like that? How can I find the value of 'constant' in that instance?

Thanks

Answer 1

Add ‘constant’ to your argument list and use the fzero function is one approach:

z = @(x,y,constant) x + y + constant;
x = 4;
y = 4;
const = fzero(@(constant) z(x,y,constant), 1)
const =
    -8