title: Replacing matrix columns in R
body: <p>I created a matrix in R</p>
  
  <pre><code>C&lt;-matrix(c(0),nrow=6,ncol=6,byrow = FALSE)
  </code></pre>
  
  <p>Now I would like to replace the first column of the matrix with the value 1, the second and third column with standard normal random variables and the last three columns with the values of an other matrix. </p>