--- /dev/null
+# Compute the sum of (normalized) sum of squares of closest distances to a medoid.
+computeDistortion <- function(series, medoids)
+{
+ n <- ncol(series)
+ L <- nrow(series)
+ distortion <- 0.
+ for (i in seq_len(n))
+ distortion <- distortion + min( colSums( sweep(medoids,1,series[,i],'-')^2 ) / L )
+
+ sqrt( distortion / n )
+}