What iteration method to use?

My problem is this:

I have a target value for x and I have to make an initial guess for y because it's unknown at the beginning. Then I make several calculations and finally get a calculated value for x. If my new x is not the same as the target value x I increase or decrease value y by certain small step and repeat all calculations until I find the solution for x.

I hope you get the idea without code. I tried doing this with while loop. It works but if my initial guess for y is far from the actual solution this may require lot's of iterations. My model will have several similar iterations loops so I wonder if there is more efficient iteration method available in Matlab? I'm new with Matlab and so far I haven't found the right tool for this.

Answer 1

[John D'Errico]

Why would you do this using a loop? You want to solve for the value of y, such that the value of

f(y)-x_target=0

Read the help and examples for fzero.

doc fzero

[Teme]

I don't want to use a loop, I want to use something like fzero :) That seems to be what I was looking for. Thanks!