clustering with NA values in R

Question

I was surprised to find out that clara from library(cluster) allows NAs. But function documentation says nothing about how it handles these values.

Answer 1

By looking at the Clara c code, I noticed that in clara algorithm, when there are missing values in the observations, the sum of squares is "reduced" proportional to the number of missing values, which I think is wrong! line 646 of clara.c is like " dsum *= (nobs / pp) " which shows it counts the number of non-missing values in each pair of observations (nobs), divides it by the number of variables (pp) and multiplies this by the sum of squares. I think it must be done in other way, i.e. " dsum *= (pp / nobs) ".