title: Convert multiple columns of a data frame from string to numeric in R
body: <p>I have a data frame contain 10 columns of data (temperatures, humidity values etc.). R identifies those as strings. I used the following command to convert one of the columns to numeric format: </p>
  
  <pre><code>df$temp_out = as.numeric(df$temp_out)
  </code></pre>
  
  <p>The problem is that i have another 7 columns which also need to be converted. I could do it for each and everyone of these, but I need to do it in approximately 50 df, so it's kind of inconvenient. Any help is welcome! </p>