How can I pass additional parameters to a function I defined?

Hello,

When using an odexx solver I know i can pass additional parameters following this structure (example for ode45)

[T,X] = ode45(f,tspan,x0,[],u,d,par)

where u,d and par are the additional parameters I am passing to ode45.

Is there any way to do the same for a function I defined? As an example, I have the following function

[t,x] = FoxRabbit_Euler_v1(f1,tspan,x0,n);

In this case f1 has some parameters I will like to pass when using "FoxRabbit_Euler_v1".

Any help will be very much appreciated

Answer 1

[Ryan Livingston]

You may want to have a look at varargin:

http://www.mathworks.com/help/matlab/ref/varargin.html

Defining a function like

 function out = foo(a,b,varargin)
 ...

allows you to require a and b as arguments then allows the user to pass along anything else. These other arguments are put into the cell array varargin and can be retrieved from there:

 if (nargin >= 3)
   extraInput1 = varargin{1};
 elseif (nargin >= 4)
   extraInput2 = varargin{2};
 ...
 end

[mauricio]

This is exactly what I needed !

Thanks a lot Ryan ! :)

[Ryan Livingston]

My pleasure mauricio and thanks for the gratitude.

[mauricio]

I think I have found the way to use varargin for my particular purpose but there is still a small issue.

I have written the following code just to understand a little better the use of varargin

function s = h(x,varargin)

y=[varargin{:}]
h=y(1)-y(2)
x
end

Here I turn the cell array into a vector and then I use the components of that vector to do something else (a difference in this case). I have play with some scalars and everything is good.

Now I have a new issue. Some of this additional parameters are scalars, others are vectors. i.e (2,[1 3],5). How can I assign each component of the array varargin into a specific variable/parameter inside my code? i.e

u=2
t=[2 3]
par=4

Any hint? Thanks for your time

[mauricio]

I tried the following function

function s = add(x,varargin)

a = [varargin{1}]
b = [varargin{2}]
c = [varargin{3}]
x
end

and when called add(1,[3 4],6,7) I get the needed result

a = 3     4
b = 6
c = 7
x = 1

Now I can use a,b,c (the additional parameters) inside my original function ;) I do not know if this is the correct way to do it or the most efficient way to use the extra parameters passed to a function, so any comment or suggestion will be very welcome.

Answer 2

[Shashank Prasanna]

You can use anonymous functions to achieve just that:

http://www.mathworks.com/help/optim/ug/passing-extra-parameters.html#brhkghv-9

Although the above link is from the optimization toolbox the concept is the same and is a pretty standard way across matlab toolboxes to pass additional parameters.

The following should be helpful too:

http://www.mathworks.com/help/matlab/math/parameterizing-functions.html

[mauricio]

Thanks Shashank ! In particular the Parameterizing Functions info will help me in the near future ;)