How to use arrayfun with a function having two vector arguments?

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Mr M. 2016-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/307836-how-to-use-arrayfun-with-a-function-having-two-vector-arguments

评论： Andrei Bobrov 2016-10-18

I have a function f(W,x), where W is a matrix and x is a vector. I would like to use arrayfun to calculate the f(W,x) for several x but constant/fix W. What is the syntax?

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Answer 1

Andrei Bobrov 2016-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/307836-how-to-use-arrayfun-with-a-function-having-two-vector-arguments#answer_239541

编辑：Andrei Bobrov 2016-10-18

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fW = @(x) f(W, x);
out = cellfun(fW,{x1,x2,x3},'un',0);

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Adam 2016-10-18

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Well, did you try doing what the error suggests?! Set 'UniformOutput' to false:

out = cellfun(fW,{x1,x2,x3}, 'UniformOutput', false);

Andrei Bobrov 2016-10-18

OK. Corrected.

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Answer 2

Rani V.S 2016-10-18

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    A = arrayfun(FUN, B, C,  ...) evaluates FUN using elements of arrays B,
    C,  ... as input arguments.  The (I,J,...)th element of A is equal to 
    FUN(B(I,J,...), C(I,J,...), ...).  B, C, ... must all have the same size.

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Answer 3

Guillaume 2016-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/307836-how-to-use-arrayfun-with-a-function-having-two-vector-arguments#answer_239533

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%W = [.,.,.;.,.,.;.,.,.]; %matrix
%x = [.,.,.,.,.,.];  %vector
result = arrayfun(@(xelem) f(W, xelem), x);  %possibly with 'UniformOutput', false, if f output is not scalar

Or if you want to be more explicit

%W = [.,.,.;.,.,.;.,.,.]; %matrix
%x = [.,.,.,.,.,.];  %vector
fW = @(x) f(W, x);  %W must exists before this line. Changing W after this line will not affect fW
result = arrayfun(fW, x);

In either case you're creating a new function (with no name in the first case, fW in the second) that binds the matrix W to f and still takes x as an input. You're then using that function in arrayfun to apply it to each element of x.

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Mr M. 2016-10-18

That is OK, but I have x1 vector, x2 vector, x3 vector, ... and I want to apply fW thru arrayfun once. Is it possible?

Guillaume 2016-10-18

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Well, first you shouldn't have numbered variables x1, x2, etc. Instead you should have just one variable which is a cell array of vectors. In that case, use cellfun:

x = {x1, x2, x3};  %you really shouldn't create the xi to start with. Put their content in the cell array as you create it.
result = cellfun(@(xv) f(W, xv), x, 'UniformOutput', false);

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