calculates the geomentric mean of data elements.
y = nan_geomean(x [,DIM [,W]])
geomentric mean
dimension
first DIMENSION, with more than 1 element
weights to compute weighted mean (default: [])
is the same as y = nan_mean(x,'G' [,DIM])
features: - can deal with NaN's (missing values) - weighting of data - dimension argument also in Octave - compatible to Matlab and Octave