Writing summation inside function handle

Hey,

I have this term

u = @(x) c(1)*f(3*(x-t(1)))+c(2)*f(3*(x-t(2)))+c(3)*f(3*(x-t(3)))+c(4)*f(3*(x-t(4)))+...

c(5)*f(3*(x-t(5)))+c(6)*f(3*(x-t(6)));

inside a function I have written. What I want is to write these six terms here using summation. So how should I go about it?

[John D'Errico]

It depends. Is the function f vectorized? If it is, then the answer is simple, even trivial. But if you cannot pass a vector of elements to the function f and have f operate on each element independently, then the solution will be more complicated, and very different.

So everything depends on the function f, and since we are not told what f is or how it is written, then no definitive answer is possible.

[Saurabh Madankar]

Here f is also a function handle, a function of x (which I have defined as a linearly spaced vector) which returns a scalar value.

[Saurabh Madankar]

And yes I can't pass a vector of elements to f. It takes only one element at a time.

Answer 1

[Aneela]

Hi Saurabh Madankar,

You can make use of the “sum” and “arrayfun” MATLAB functions to write these 6 terms using summation.

u = @(x) sum(arrayfun(@(k) c(k) * f (3 * (x - t(k))), 1:6));

Refer to the following links for further details on “sum” and “arrayfun“ functions in MATLAB.

sum – https://www.mathworks.com/help/matlab/ref/sum.html?s_tid=doc_ta

arrayfun - https://www.mathworks.com/help/matlab/ref/arrayfun.html?s_tid=doc_ta