Compute the variance while ignoring NaN values.
For vector arguments, return the (real) variance of the values. For matrix arguments, return a row vector containing the variance for each column.
The argument opt determines the type of normalization to use. Valid values are
- Normalizes with N-1, provides the best unbiased estimator of the variance [default].
- Normalizes with N, this provides the second moment around the mean.
The third argument dim determines the dimension along which the variance is calculated.