Use quadgk with multiple Inputs with Matlab Coder

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Hi I want to create a C file out of my Matlab file. In my Matab file I have to make some integrations, that is way I am using the quadgk function. My problem is now, that the Matlab Coder for generating the C Code doesn't allow function handels.
I want to integrate the function
function val=integrand1(x,c,d) val=x*c+d; end
by the follwing term
Integral = quadgk('integrand1',z(1),z(2),-1,z(2))
So the intergal goes from z(1) to z(2) and for the parameters c and d I want to use the values -1 and z(2). If I do so the Matlab Coder gives the errow ??? First input argument must be a function handle.
But how can I use quadgk instead? Thank you very much for any help.
Best regards Antonia

Accepted Answer

Mike Hosea
Mike Hosea on 20 Feb 2014
Edited: Mike Hosea on 20 Feb 2014
I don't have a lot of time to type this. Hopefully if it isn't clear I can come back and add some detail.
The way we normally do this in MATLAB is not with a string to represent the integrand. That is obsolete. The standard way would be integrate the anonymous function @(x)integrand1(x,c,d), where c and d would be defined before, e.g.
quadgk(@(x)integrand1(x,-1,z(2)),z(1),z(2))
Unfortunately, this won't work in MATLAB Coder because MATLAB Coder doesn't support anonymous functions. So you will have to do something a little more complicated using persistent variables, something like
function val = integrand(x,c,d)
persistent c_saved,d_saved
if isempty(c_saved)
c_saved = 0;
d_saved = 0;
end
if nargin >= 2
c_saved = c;
end
if nargin >= 3
d_saved = d;
end
val = x*c_saved + d_saved;
Then to use it, you just call it first with your desired c and d.
integrand1(0,-1,z(2));
integral = quadgk(@integrand1,z(1),z(2));
I apologize if I have made a typo or some other boneheaded error above. I don't have time to test it, but we test QUADGK for code generation using this basic approach, so I know it can work. -- Mike
  5 Comments
Tunga Rangaswamy
Tunga Rangaswamy on 16 Oct 2019
Thanks Steven!
My question is also based on anonymous function and MATLAB coder which seemed aligned to the previous question. However, I have asked this a separate question now and I am looking forward to an answer.

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