title: Modify each row of an R data frame
body: <p>I have a data frame and a function that are both too complicated for an example, but all I want to do is modify each row in the data frame. The function simply takes a vector and modifies some of the values based on the other values, the dimensions remain the same.</p>
  
  <pre><code>newt = data.frame()
  for(i in 1:nrow(t)){
    row = t[i,]
    newt = rbind(newt,f(row))
  }
  t = newt
  </code></pre>
  
  <p>Currently I'm using a for loop which I understand is both not the R-y way to do things and it is also exceedingly slow (I ~1million rows in my actual data). </p>
  
  <p>I'm strongly trying to avoid plyr or data.table or any other package because there is a lot of code written already around the structure I have and I'd like to avoid extra complication. Apply seems to change everything to an array or matrix but my columns are of all sorts of types so this is not an option. I tried using adply from plyr but this was not memory efficient and crashed for decent sized input.</p>