It may well be correct. -2.0 to the power of 10^15 means it is essentially zero. But as Justin just noted in the comment, you have
(sum (x - mean(x) )^2
when you probably meant:
sum( (x - mean(x) )^2 )
It may well be correct. -2.0 to the power of 10^15 means it is essentially zero. But as Justin just noted in the comment, you have
(sum (x - mean(x) )^2
when you probably meant:
sum( (x - mean(x) )^2 )