title: go through a dataframe in R reading it by columns
body: <p>I would like to read each element (and convert it from character to numerical) from column 2 onwards in my dataframe. I have set up this code, but I cannot understand why it is incorrect. May you help me please? I am new with R.</p>
  
  <pre><code>for(i in mydata[,-1])
      for(j in mydata[,i])
          type.convert(mydata[j,i], na.strings='NA',as.is = TRUE, dec = '.')
  </code></pre>