# how to check if there are any elements are equal in a vector

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xueqi on 10 Jun 2013
Dear fellows,
Do you know how to write a code to check if are there any (Given that I don't know the numbers)elements are equal in a vector? And then read the element.
Many thanks, Xueqi
Azzi Abdelmalek on 10 Jun 2013
Please, make it simple, provide a short example, and tell what should be the result

Jan on 10 Jun 2013
The question is still not clear. Perhaps you want:
nonZero = x(x ~= 0);
anyDuplicates = length(unique(nonZero)) ~= length(nonZero);
Or equivalently:
anyDuplicates = ~all(diff(sort(x(x ~= 0))));

Daniel Shub on 10 Jun 2013
There is no built in function that will do that. You could test the number of unique elements in the vector against the length of the vector
f = @(x)isequal(length(x), length(unique(x)))
I am not sure what you mean by read the element, especially if more than one element is duplicated. Maybe something like
y = 1:length(x);
y(sort(b)) = [];
x(y)
xueqi on 10 Jun 2013
c is a dynamic vector, the element of c(i) is decided by previous elments c(i-1). For example
if true
% 0
0.231095363111135
0
0
0.400000000000000
0
0
0
0.400000000000000
0
0.400000000000000
0.857374060834467
0.0314599355591159
0
0
0
0
0
0
0.446800862782801
end
See in this vector, c(10) should be equal to 0.4 since 0.4 has been shown up for twice previously. But it is still 0...

Image Analyst on 10 Jun 2013
Are they integers, or at least doubles or singles with perfectly, exactly integer values? Do whos() or class() to find out. If they're not integers, you'll have to see if they're within some small tolerance. See the FAQ : http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F for discussion and code example.
xueqi on 10 Jun 2013
Hi, they are not integers. The elments comes from a simulation from the uniform distribution. The point is if there is any two are equal(if are not 0) then it must has be the same pre-speficied value which is 0.4.