wssplot<-function(data,nc=15,seed=1246){

  wss<-(nrow(data)-1)*sum(apply(data,2,var))

  for(i in 2:nc){

    set.seed(seed)

    wss<-sum(kmeans(data,centers=i)$withinss)}

  plot(1:nc,wss,type="b",xlab="Number of Clusters",

       ylab="Within groups sum of squares")}

这位大佬，这段代码的含义是什么意思