Combining function handles into one function handle
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Is there a convenient way where I can combine N SISO function handles to create one SIMO function handle?
For example of N=2, if I got:
a = @(x) x(1)^2+x(2)^2;
b = @(x) x(3)^2-x(4)^2;
I would like to create a single function handle like:
c = @(x) [x(1)^2+x(2)^2; x(3)^2-x(4)^2];
Thanks in advance!
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Answers (2)
Fangjun Jiang
on 4 Aug 2020
>> a = @(x) x(1)^2+x(2)^2;
b = @(x) x(3)^2-x(4)^2;
>> a(1:4)
ans =
5
>> b(1:4)
ans =
-7
>> c = @(x) [x(1)^2+x(2)^2; x(3)^2-x(4)^2];
>> c(1:4)
ans =
5
-7
>> d=@(x) [a(x);b(x)]
d =
function_handle with value:
@(x)[a(x);b(x)]
>> d(1:4)
ans =
5
-7
>>
5 Comments
Fangjun Jiang
on 4 Aug 2020
Edited: Fangjun Jiang
on 4 Aug 2020
treat the function handles the same as strings, as in cellstr(). You can't put function handles in a regular array, but you can put them in a cell array.
suppose you have function handles defined in f{1}, f{2}, f{3}, ..., f{n}
then at any iteration k, your SIMO function handle is d=f(1:k). Again, it is a cell array of function handles. If you want to use this function handle cell array d to evaluate without for-loop, Bruno Luong has provided answer below. I can just use a simple example:
%%
f{1}=@(x) x(1)^2+x(2)^2;
f{2}=@(x) x(3)^2-x(4)^2;
f{3}=@(x) x(1)*x(4);
y=1:4;
for k=1:numel(f)
d=f(1:k);
out=@(x) cellfun(@(f) f(x), d);
result=out(y)
end
result =
5
result =
5 -7
result =
5 -7 4
Bruno Luong
on 4 Aug 2020
Edited: Bruno Luong
on 4 Aug 2020
a = @(x) x(1)^2+x(2)^2;
b = @(x) x(3)^2-x(4)^2;
c = @(x) x(1)*x(4);
% suppose your for-loop puts each function handle in a cell array like this
allfun = {a, b, c};
vecfun = @(x) cellfun(@(f) f(x), allfun(:));
x = rand(1,4);
a(x)
b(x)
c(x)
vecfun(x)
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