Cluster Analysis

Cluster Analysis

Formatting the Data

> mydata <- na.omit(mydata) # listwise deletion of missing
> mydata <- scale(mydata) # standardize variables

#  (Opyional) Determine number of clusters
> wss <- (nrow(mydata)-1)*sum(apply(mydata,2,var)) for (i in 2:15)
> wss[i] <- sum(kmeans(mydata, centers=i)$withinss)
> plot(1:15, wss, type="b", xlab="Number of Clusters", ylab="Within groups sum of squares")

Kmeans Clustering

> fit <- kmeans(mydata, 5) # 5 cluster solution
# get cluster means 
> aggregate(mydata,by=list(fit$cluster),FUN=mean)
# append cluster assignment
> mydata <- data.frame(mydata, fit$cluster)