How to check for identical Vectors concurrently? - matlab

Question

Trying to check for identical vectors. Currently using the isequal function to check for identical ones.
It runs like this.
if isequal (vectorA, vectorB) == 0
It will then run an instruction.
end
if isequal (vectorA, vectorB) == 1
It will run another instruction.
end
I now have a set of vectors more from A to F. Is there anyway to check all of them (B,C,D,F) against Vector A and do the same thing as mentioned?
Meaning
if vectorA matches any of B,C,D,F == 0
The same with the second case where
if vectorA matches any of B,C,D,F == 1
The vectors are constantly changing and this is running in a loop to check for identical vectors. Seems like the isequal function only works between 2 Vectors.
all the vectors are 1xi where i can be a number up to 50
ANY help in this would be greatly apreciated!

Answer 1

I suggest you keep your other vectors in a matrix rather so something like:
a = vectorA;
B = [vectorB, vectorC, vectorD, vectorE];
Then just use a simple for loop:
flag = false;
for k = 1:size(B,2)
flag = flag || isequal(a,B(:,k));
if flag
break
end;
end
or if you prefer a completely vecotrized one-liner over the loop (but in this case, I suspect the early exit clause in the loop might actually provide a performance benefit, depends on your data though):
flag = any(all(bsxfun(#eq,a,B)))
then
if flag
%// do stuff if any was equal
else
%// Do stuff if none were equal to a
BTW if you wanted to check if they ALL match instead of if ANY match then change to:
flag = all(all(bsxfun(#eq,a,B)))
or in the loop change to
flag = true;
for k = 1:size(B,2)
flag = flag && isequal(a,B(:,k));
if ~flag
break
end;
end

Answer 2

This can be done very easily with ismember:
To check whether it a vector matches any of the rows:
v = 1:3
M = [1:3;2:4;3:5]
ismember(v,M,'rows')
To check whether it matches all of the rows, you can extend it by also checking something like:
size(unique(M,'rows'),1)==1
This assumes that the vectors are stacked below each other, but of course it is easily adjusted to match the situation when they are next to each other.

Answer 3

To check if A equals any of B, C, D, F (with possibly different sizes), use cellfun on a cell array containing your vectors:
if any(cellfun(#(x) isequal(A,x), {B,C,D,F}))
If all vectors are row vectors with an equal number columns, it may be faster to use bsxfun on a matrix containing your vectors:
if any(all(bsxfun(#eq, A, [B; C; D; F]).'))