why eq says they are not equal

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I have two equal vectors a = b. When I check for equality:

y = eq(a, b)
find(y==0)

I get most of values, meaning they are NOT equal.

What would be the reason for this?

N.

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Nuchto 2012-7-22

Thanks, I did.

Jan 2012-7-22

@Nuchto: Is your problem solved?

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Answer 1

Muruganandham Subramanian 2012-7-19

编辑：Walter Roberson 2012-7-22

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Hi Nuchto,

Check this below link:

http://www.mathworks.in/help/techdoc/ref/eq.html

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Nuchto 2012-7-19

I have checked the help, but it didn't answer to my question.

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Answer 2

Jan 2012-7-19

编辑：Jan 2012-7-19

在 MATLAB Online 中打开

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To compare two vectors use:

r = isequal(a, b)

or to find the difference between vectors (or other arrays) of the same size:

any(a - b)

Note, that the later replies FALSE even for ones(1,10) and ones(1,1).

If you only assume, that the vectors have equal values, check a - b and note, that the limited precision of the type double leads to effects like:

03. - 0.2 ~= 0.1

Then check "almost equal" by:

limit = eps(max(max(abs(a(:)), abs(b(:)))));
% or:   eps(max(abs(a(:)), abs(b(:))));
% or:   the same times 10
a_eq_b = isequal(size(a), size(b)) & all(abs(a - b) < limit);

The choise of the limit depends on the physical meaning of the variables. There is no unique definition to distinguish measurement noise from noise caused by numerical artifacts for a tiny values.