- | Weighted variance. This is biased estimation.
varianceWeighted :: (G.Vector v (Double,Double)) => v (Double,Double) -> Double
varianceWeighted samp
    | G.length samp > 1 = fini $ robustSumVarWeighted samp
    | otherwise         = 0
    where
      fini (V s w) = s / w
{
varianceWeighted :: (G.Vector v (Double,Double)) => v (Double,Double) -> Double
varianceWeighted samp
    | G.length samp > 1 = fini $ robustSumVarWeighted samp
    | otherwise         = 0
    where
      fini (V s w) = s / w

varianceWeighted samp
    | G.length samp > 1 = fini $ robustSumVarWeighted samp
    | otherwise         = 0
    where
      fini (V s w) = s / w
