title: subset data frame by skipping a specific number of rows
body: <p>i have a very big data frame((35000 line) but i want to get specific rows by skipping for example 100 row.</p>
  
  <p>so in this case each 100 row I'll just get one row.</p>
  
  <p>i know that it can be done using:</p>
  
  <pre><code>N = nrow(dataframe)
     for( i in seq(1:N,by=100))
     { 
     out &lt;- rbind(out, data.frame(...)
  
      }
  </code></pre>
  
  <p>is this can be done more easily than a for loop?? using <code>subset</code> or something like this</p>
  
  <p>regards</p>