random equation fitting to data set and finding constant parameters

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aditi
aditi 2014-1-22
评论： Walter Roberson 2017-10-21
I have x and y coordinates and I want to fit an equation:
y=a*exp(x^b - 2^b)
to the data set and thus finding parameters a and b. Please help me through it.

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采纳的回答

Amit
Amit 2014-1-22
First make a function that you'll use to fit like this:
function val = myfunc(par_fit,x,y)
% par_fit = [a b]
val = norm(y - par_fit(1)*exp(x.^2-2^par_fit(2)));
Now, find the parameters like:
my_par = fminsearch(@(par_fit) myfunc(par_fit,x,y),rand(1,2));
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aditi
aditi 2014-1-23
okay...i will follow previous instructions carefully...maybe i have done something wrong...
and a big thanks to u amit...u were of great help :) will contact u if m stuck again somewher else thanks
aditi
aditi 2014-1-23
one more thing...what i found after googling is that in such cases u have to give a specific range for 1 of the parameter... so any idea about that..??
like in above equation if i deliberately want that the b value should lie betweem 0.2 and 2 and then find a and b...how can i do that???

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Matt J
Matt J 2014-1-22
You might also try FMINSPLEAS. It can take advantage of the fact that y has a linear dependence on one of the parameters 'a'.
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Sneha Roy
Sneha Roy 2017-10-21
编辑：Sneha Roy 2017-10-21
for some reason the variable par_fit is undefined error doesn't go away. How did you solve that error?

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