Finding if a vector is a subset
조회 수: 16(최근 30일)
I am trying to build a function that for
a=[1 2] b=[1 3 2 9 5]
will return false
a=[1 2] b=[1 2 2 9 5]
What I manage to do is
function[yn] = subset1(v1,v2)
if length(find(v))==length(find(v1)) && find(v)==find(v1)
if length(find(v))==length(find(v2)) && find(v)==find(v2)
but it does not work in the first case
Roger Stafford 2018년 4월 10일
The following should be faster:
m = size(a,2);
n = size(b,2);
for k = 1:n-m+1
s = all(a==b(k:k+m-1));
if s, break, end
Logical s will be true if any m-length section of b is equal to the a vector.
Rik 2018년 4월 10일
strfind should be an option, especially if you only have positive integer scalars, which you can just cast to char. Otherwise, the solution below might also be an option. It might not scale really well to huge vectors due to that convolution, but that is done on a binary matrix, so that should be as fast as it can be.
Another note: this uses implicit expansion, so if you don't have R2016b or newer, you'll have to use bsxfun.
a=[1 2];b1=[1 3 2 9 5];b2=[1 2 2 9 5];
%requires implicit expansion (use bsxfun on R2016a and earlier)