How to solve the problem that the demeaning of X gives a variable Y that has not exactly a zero mean, probably due to very small values ?

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Fox
Fox 2018-6-8
回答： Sam Cook 2018-6-13
Hello together, I have the problem that I want to standardize a vector X. I do this by firstly demeaning X.
if true
% Y=(X-mean(X))
end
However now I have the problem that the mean of Y is not exactly zero like it should be, but really close to zero like 1.8*e-18. I attached the values of X as a file here. If I only considereing the first 6 values of X its fine
Y=(X(1:6)-mean(X(1:6)),
mean(Y)=0
but if I include the really small value of X(7), I get this different result.
if true
% Y=(X(1:7)-mean(X(1:7)),
mean(Y)=1.8e-10
end
Does anybody of you know what matlab is doing here? (rounding problem, too small number...)

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采纳的回答

Sam Cook
Sam Cook 2018-6-13
This is a result of the accuracy of floating-point numbers. If you need to account for this, you can use the eps function to determine the degree of accuracy you are working with.

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