We know that the iris data set include three species. K-means does a pretty good job of correctly identifying correct groups.
data(iris) cl <- kmeans(iris[,1:4], 3) cl$cluster cbind(1:150,iris$Species)
cl$cluster reveals which group each observation was placed in; compare this with a listing of the species designations mapped next to 150 index values (cbind(1:150,iris$Species)).
If you would like to plot each cluster, you can set plot's "col" to the cl$cluster vector, coloring each observation with the integer based on the cluster analysis.
plot(iris[,1:4], col = cl$cluster)