wsplot<-function(data, nc=15, seed=1234){
wss<-(nrow(data)-1)*sum(apply(data, 2, var))
for(i in 2:nc){
set.seed(seed)
wss[i]<-sum(kmeans(data, centers=i)$withinss)
}
plot(1:nc, wss, type="b", xlab="Number of Clusters", ylab="Within groups sum of squares")
}