# Definite integral in (embedded) Matlab function, with passing additional parameters to the integrand

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Hi,

I have a simulation file to model the dynamic behaviour of system, at each time step , I need to evaluate a time-independent integral. To do so I use (embedded) Matlab function but I got many errors. Any help would be appreciated.

inside my (embedded) Matlab function is:

%%________________ method one

function forces=my_embeded_func(positions)

y1=position(1);

y2=position(2);

forces=integral(@(theta),y1+y2*theta,0,2*pi)

end

%_______________

Notes: 1-my integrand is actually very complicated but I put something simple here.

2-I have been told to use "quadgk" instead of "inregra;", but it did not worked

3- I also tried the following method but it did not helped!

%%________________ method two

function forces=my_embeded_func(positions)

coder.extrinsic('myFunc')

y1=position(1);

y2=position(2);

forces=myFunc(y1,y2)

end

% where

function a=myFunc(y1,y2)

a=quadgk(@(theta),y1+y2*theta,0,2*pi)

end

%_______________

Thanks,

Ehsan

##### 0 Comments

### Accepted Answer

Mike Hosea
on 18 Dec 2014

Edited: Mike Hosea
on 18 Dec 2014

If you don't need to generate code for your model, I think you can use your second approach, but you need to fix a few unrelated errors. Put myFunc into a MATLAB file myFunc.m. There is a syntax error. Remove the comma between @(theta) and y1:

function a=myFunc(y1,y2)

a=quadgk(@(theta)y1+y2*theta,0,2*pi)

end

Now let's consider your block code. I didn't know whether you meant for your variable to be called "positions" or "position". I just picked one. Second, to call an extrinsic function, you have to pre-allocate the output to tell the compiler how to interpret the mxArray that comes back from MATLAB. The block code should look something like this:

function forces=my_embeded_func(position)

coder.extrinsic('myFunc')

y1=position(1);

y2=position(2);

% Define the output type for myFunc, in this case a scalar double.

forces=0;

% Evaluate myFunc in MATLAB.

forces=myFunc(y1,y2)

end

If you do need to generate code, the way I tell people to do this is to use persistent variables to store the parameters of the function. The whole thing could go into the block.

function forces=my_embeded_func(position)

y1=position(1);

y2=position(2);

forces=myFunc(y1,y2);

end

function a=myFunc(y1,y2)

integrand('set positions',y1,y2);

a=quadgk(@integrand,0,2*pi);

end

function v = integrand(theta,y1set,y2set)

persistent y1 y2

if isempty(y1)

y1 = 0;

y2 = 0;

end

% More than one input means we are setting the persistent

% parameter values, not evaluating the integrand function

% on this particular call. The theta argument is ignored.

% We make it a string 'set positions' in the calling code

% solely for readability.

if nargin > 1

y1 = y1set;

y2 = y2set;

% nargout had better be zero, since we haven't set v.

return

end

v = y1 + y2*theta;

end

##### 2 Comments

Mike Hosea
on 19 Dec 2014

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