I want to calculate each column's sample devia

问题:

I am doing cluster analysis based on data "college" which consists of 3 nominal and 20 numeric variables.

# select the columns based on the clustering results
cluster_1 <- mat[which(groups==1),]

#"cluster_1" is a data set which is made by cluster analysis consisting of 125 observations.


rbind(cluster_1[, -(1:3)], colMeans(cluster_1[, -(1:3)]))
#This is process of calculating each column's mean and attach the means to the bottom of the data set, "cluster_1".

Now what I want to know is how to calculate each column's sample variance and sample deviation and how to attach them to the bottom of the data set "cluster_1".

Please let me know.

回答1:

  rbind(cluster_1, apply(cluster_1,2,sd), apply(cluster_1, 2, var) )