let's say we have function like below:
function Output=DoSomething(f)
...
...
end
where 'f' is a function that user inputs , like 'sin(t)' , 'x^2' or a vector of functions. the function DoSomething gets f and perform some operation on it. for example, evaluates 'f' at t=pi/2,pi,2*pi,... and put result in Output vector. how can this be done in MATLAB? should f be an string variable? if yes, does it need to convert to another data type? i'm getting errors doing this.
A couple of example ways to do this
Make the input f a function handle
function [output] = dosomething(f, varargin)
output = f(varargin{:});
end
>>f = @(x, y) sqrt(x.^2 + y.^2);
>>dosomething(f, [3 5 8], [4 12 15])
>>ans =
>>5 13 17
Make f a string, and use 'eval' (first is better practice, I think, this second one fails if nargin is less than 2, but not if nargin is >=3 even though the function doesn't use them.)
function [output] = dosomething(f, varargin)
output = eval(f);
end
>>f = 'sqrt(varargin{1}.^2 + varargin{2}.^2)';
>>dosomething(f, [3 5 8], [4 12 15])
>>ans =
>>5 13 17
If you want to be able to input multiple functions, you can do something like
function [output] = dosomething(f, varargin)
output = cellfun(@(x) x(varargin{:}), f, 'UniformOutput', false);
end
>> f{1} = @(x, y) sqrt(x.^2 + y.^2);
>> f{2} = @(x, y) atan2(x, y);
>> A = dosomething(f, [3 5 8], [4 12 15]);
>> A{1}
ans =
5 13 17
>> A{2}
ans =
0.6435 0.3948 0.4900
Wasn't sure whether to make this a comment or an answer...
It's really difficult to do this as there are all sorts of different ways of inputting functions into Matlab. I think that the easiest thing to do would be to make f an anonymous function, e.g.
f=@(x,y) x.^2+y.^2;
then inside the DoSomething function you can do f(1,2) or f(1:10,11:20).
Note if the function is not defined using element-by-element operation (.*, etc.) then you can convert it so that it can take vector arguments by doing
syms q w
f=matlabFunction(f(q,w),'vars',[q w]);
which could prove useful.
Even if you don't make f an anonymous function for the input into DoSomething, converting whatever you get into either an anonymous function or a vector of values of f is probably a good idea in terms of performance.
