MATLAB: varargin (cell) not compatible with fminsearch (double)? - matlab

Question

I have functions I've built using variable arguments but now I want to optimize these functions. However, in the current form, varargin doesn't seem to work well with FMINSEARCH? What can I do? Is there something wrong?
I am trying to do the following:
y = #(varargin)-fn_backtest_v0002(varargin{:});
start = {3,0,0.5,10,0.05,0,1,1};
max = fminsearch(y,start);
But I get this error:
Error using fminsearch (line 96)
FMINSEARCH only accepts inputs of data type double.
From the simple examples of FMINSEARCH, a vector should be used, however I have varargin in my functions which require arguments to be of cell type.
Any help appreciated.

Answer 1

You should write a wrapper function that accepts vector as parameter and passes them in the format that fn_backtest_v0002 expects to get. For example:
function out = fn_backtest_v0002(varargin)
.... %Your code here
end
And the wrapper function:
function out = fn_backtest_v0002_wrapper(vec)
out = -fn_backtest_v0002(num2cell(vec));
end
Then, you can use the wrapper function with fminsearch :
start = [3,0,0.5,10,0.05,0,1,1];
max = fminsearch(y,#fn_backtest_v0002_wrapper);
Another alternative is to re-write fn_backtest_v0002 to have vector input arguments (Which makes much more sense than varargin in your case.

Answer 2

Thanks to Andrey for idea of wrapper function. (I am a programming newbie).
This is exactly how I did it.
Create wrapper function:
function [ out ] = fn_backtest_v0002_wrapper( vec )
cell = num2cell(vec);
out = fn_backtest_v0002(cell{:});
end
Then I can run the following commands successfully:
y = #(vec)-fn_backtest_v0002_wrapper(vec);
start = [3,0,0.5,10,0.05,0,1,1];
max = fminsearch(y,start);