How to convert a cell array containing various inline functions to a unique inline function?

I need to use the fminimax function and the input has to be necessarily a single inline function. But I need several equations in this function. And I'm going to add them one by one through a for loop in a cell.

I need to convert this:

cell =
  1×3 cell array
    {@(x)(a(1,1)-x)^2}    {@(x)(a(2,2)-x)^2}    {@(x)(a(3,3)-x)^2}

For this:

func =
  function_handle with value:
    @(x)[(a(1,1)-x)^2;(a(2,2)-x)^2;(a(3,3)-x)^2]

Answer 1

[Stephen23]

You could hide the loop inside cellfun:

>> a = rand(3,3);
>> C = {@(x)(a(1,1)-x)^2,@(x)(a(2,2)-x)^2,@(x)(a(3,3)-x)^2};
>> F = @(x)cellfun(@(f)f(x),C(:));
>> F(1.2)
ans =
   0.40767
   0.39542
   1.26850

Answer 2

[TADA]

You can generate a function handle which will execute all the handles in a cell array using closures:

a = magic(3);
myFunctions = [{@(x)(a(1,1)-x)^2}    {@(x)(a(2,2)-x)^2}    {@(x)(a(3,3)-x)^2}];

aggregatedFunctionHandle = genFunHandle(myFunctions);

disp(aggregatedFunctionHandle(10));

function foo = genFunHandle(handles)
    function y = func(x)
        y = cellfun(@(fh) fh(x), reshape(handles, numel(handles), 1));
    end

    foo = @func;
end

output:

        6724
        4900
        6084

but if your functions are always of that format: @(x)(a(i,i)-x)^2

do this instead:

f = @(x) (diag(a)-x).^2

[TADA]

also possible with an inline closure like that:

a = magic(3);
myFunctions = [{@(x)(a(1,1)-x)^2}    {@(x)(a(2,2)-x)^2}    {@(x)(a(3,3)-x)^2}];

aggregatedFunctionHandle =...
    @(x) cellfun(@(fh) fh(x), reshape(myFunctions, numel(myFunctions), 1));