y=lab.var(x) returns a tensor y of the standard deviation of the elements in each column of x.

lab.var(x) normalizes by (n-1) where n is the number of elements. This makes lab.sum(lab.var(x)) the best unbiased estimate of the variance if x is a sample from a normal distribution.

y=lab.var(x,true) performs the var operation normalizing by n instead of n-1.

y=lab.var(x,false) performs the var operation normalizing by n-1.

y=lab.var(x,flag,n) performs the var operation over the dimension n.