How do I vectorize a sum involving an anonymous function?

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Norman
Norman 2014-8-11
回答： Michael Haderlein 2014-8-11
Hi
I have a sum that involves an anonymous function g of the form
beam = sum_{k=-K}^{k=K} A(k) g(x-c(k))
where A and c are know vectors of length n. I would like to be able to pass beam a vector x of length m ~= n AND vectorize the result. I have tried arrayfun, but get dimension mismatches. Is there any way to implement this without resorting to a loop?
Thank you
Norm

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回答（2 个）

Iain
Iain 2014-8-11
Tricks to try: bsxfun, summation along the right column/row, replicating matrices as needed (repmat)
Michael Haderlein
Michael Haderlein 2014-8-11
So you have a matrix g, right? Then, you don't need to sum by hand but just multiply g*A. Such as
>> x=(1:4)';
>> k=0:5;
>> A=k'.^2;
>> g=x*sqrt(k);
>> g*A
ans =
110.1470
220.2940
330.4410
440.5880
In this example, the first value 110 is g(x(1),k)*A(k) and so on:
>> sum(g(1,:).*A')
ans =
110.1470

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