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cfit object in function handle

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Philip Croné
Philip Croné on 29 Apr 2020
Edited: Adam Danz on 29 Apr 2020
I have constructed a curve fit "func" with the following line.
func=fit(x,y,'pchipinterp')
Now I want to use "func" inside an anonymous function as e.g
func2= @ (x,c) x-(c*x+x^2)/func(x)
Then I want to find the root of func2=0 using e.g FZERO as
c=2;
func3=@ (x) func2(x,c)
sol=fzero(func3,<interval>)
Could it be causing any trouble that i am using a cfit object inside the function "func2" ? My solution output is making me suspicious. Note that func2 is not the actual function i'm using but of a similar form.
Any help is much appreciated!
Best regards

  1 Comment

Adam Danz
Adam Danz on 29 Apr 2020
"I am not sure this is a correct way of doing it ..."
Doing what?
"...because the solution is not what at all what you would expect?"
What is the solution and what do you expect?
We obviously cannot run the code nor do we know what the solution is or what you expect the solution to be.

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Accepted Answer

Adam Danz
Adam Danz on 29 Apr 2020
My blind guess is that x or c is a vector in which case,
func2= @ (x,c) x-(c.*x+x.^2)./func(x)
% ^ ^ ^

  4 Comments

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Adam Danz
Adam Danz on 29 Apr 2020
As long as the cfit obj is defined prior to the anonymous function, there are no problems with that. You can think of the cfit obj as a function. You're providing it with inputs and it produces outputs.
Whatever you're seeing that makes you suspicious, it's not because you're using a cfit obj within an anonymous function.
Adam Danz
Adam Danz on 29 Apr 2020
Whenever you have a suspicion, simplify the problem and test it with known inputs and outputs.
% Create a cfit object
f = fittype('a*x');
c = cfit(f,2); % This just multiplies x by 2
% Create anon function that uses the cfit obj
fun = @(a,x) c(x) + a; % multiply x by 2 and add a
% Test it with known inputs
fun(10,[2 4 6])
ans =
14 % 2*2 + 10
18 % 4*2 + 10
22 % 6*2 + 10
Philip Croné
Philip Croné on 29 Apr 2020
Thank you!
Best regards

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