title: I want to calculate each column's sample deviation in data
body: <p>I am doing cluster analysis based on data "college" which consists of 3 nominal and 20 numeric variables. </p>
  
  <pre><code># select the columns based on the clustering results
  cluster_1 &lt;- 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".
  </code></pre>
  
  <p>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".</p>
  
  <p>Please let me know.</p>