Getting x value for a given y value from a fitted model

12 views (last 30 days)
Hi,
I have my code:
curve = @(a, b, c, d, e, x) a./(b+exp(-c*(x-d)))+e;
lower_bound = [-Inf -Inf -Inf 0, 0];
upper_bound = [Inf Inf Inf max(x), max(y)];
starting_param = [max(y) 1 1 x(round(length(x)/2)), min(y)];
sigm=fit(x, y, curve, 'StartPoint', starting_param, 'Lower', lower_bound, 'Upper', upper_bound) ;
I'm getting my fit result in the sigm which is cfit type.
My question is: how to obtain x value from a given y value out of sigm? If I write ans=sigm(0.5) I'm getting y value for a x=0.5 What I want is to get x value for y=0.5. How to code it?
thanks for help!

Accepted Answer

dpb
dpb on 17 Jul 2013
A) Evaluate the function over a range of x and then use interp1 to interpolate over the response to find a given x that gives a desired value.
B) Use fsolve() Recast the function to form f(x)-y = 0 where y is your target value.

More Answers (0)

Categories

Find more on Multicore Processor Targets in Help Center and File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!