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

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]

Please, make it simple, provide a short example, and tell what should be the result

Answer 1

[Jan]

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))));

Answer 2

[Daniel Shub]

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]

I assume that it is impossbile for more than one element is duplicated, if both of them are not equal to 0. In the case of one element is duplicated and also the number 0 is duplicated, then I need to read the one which is not 0. I write something like

if true
  % for j=1:(i-1)
          if (length(unique(c(j)))<length(c(j)))  
              c(i)=c(j);
          end
          if c(j)~=0
              break
          end

end

But it doesn't seem to work. My idea is to let the logic goes on until it find a duplication which is not equal to 0 then it can stops.

[Daniel Shub]

You are missing an end. What is c? What is i?

"But it doesn't seem to work." isn't helpful. What do you want to happen? What happens? Your logic about single duplicates and zero, doesn't make any sense to me. You need to explain it in both words and code.

[xueqi]

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...

Answer 3

[Image Analyst]

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]

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.