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 ?

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...)

Answer 1

[Sam Cook]

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.