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

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xueqi 2013-6-10

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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

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Azzi Abdelmalek 2013-6-10

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

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Answer 1

Jan 2013-6-10

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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))));

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Answer 2

Daniel Shub 2013-6-10

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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)

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Daniel Shub 2013-6-10

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 2013-6-10

在 MATLAB Online 中打开

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...

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Answer 3

Image Analyst 2013-6-10

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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.

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xueqi 2013-6-10

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.

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