Wrong mean calculation

Hello

I notice that when Matlab calculates the Standard deviation of a vector with the exact same values it doesn't returns 0! For example: Vector=ones(100,1)./3; Average=mean(Vector); STDEV=std(Vector);

Moreover if you divide the Vector by say 3456 The average is also wrong (i.e different than any value in the vector)

Thanks in advance itay

Answer 1

[David Young]

It's a rounding error. See this FAQ.

Answer 2

[Jan]

No, the calculated values are not wrong.

Calculations with doubles are performed with a limited number of digits. Therefore some rounding effects will occur. See FAQ 6.1