MATLAB Answers

How to find a combination like this

I am wondering is there a way where I could use a matrix in combinatorics such as
nchoosek(4,1:4) where it calcluates 4choose1, 4choose2,... 4choose4 ?
Is thie possible in Matlab?

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2 Answers

Answer by Walter Roberson
on 24 Feb 2019
 Accepted Answer

N = 4;
temp = factorial(0:N);
temp(end) ./ (temp .* fliplr(temp))
This would be 4C0, 4C1, 4C2, 4C3, 4C4, so you could index into the result to get the subset you need.

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temp = cumprod([1 1:N]);
turns out to be faster than factorial(0:N)

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Answer by Jos (10584)
on 1 Mar 2019

Computationally less efficient, and mathematically less beautiful as Walters' snippet, but more matlab-ish in style:
N = 4 ;
C = arrayfun(@(k) nchoosek(N, k), 0:N)
or after same mathematical adjustments to N! / K!(N-K)!
C2 = arrayfun(@(k) prod(k+1:N)/prod(2:N-k), 0:N)

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