title: Error using survSplit function
body: <p>I'm rerunning code from 2 years ago and am encountering a new error with the survSplit function. The error says that my object cannot be found, even though it is a defined column in my dataframe.</p>
  
  <p>Here is an example of my dataframe:</p>
  
  <pre><code>f12 &lt;- data.frame(id = 1:6,
                next.ivl= c(22.348, 1.837, 2.051,1.782,1.692, 1.730),
                event = c(0,1,1,0,1,1),
                enter= rep(0,6),
                end=c(22.348, 1.837,2.051,1.782,1.629,1.730))
  </code></pre>
  
  <p>My previous code was the following:</p>
  
  <pre><code>cutpoints.l &lt;- c(10/12, 1.25, 1.75, 2.25, seq(3,11))
  
  f12.split &lt;- survSplit(f12, 
                     cut = cutpoints.l, 
                     event = "event", 
                     start = "enter", 
                     end = "next.ivl", 
                     episode = "ivl")
  </code></pre>
  
  <p>I went ahead and tried running the example code provided <a href="https://stat.ethz.ch/R-manual/R-devel/library/survival/html/survSplit.html" rel="nofollow">here</a> (also below), and am getting another error ("Error in Surv(time, status) : Time variable is not numeric." These errors seem to be related. What's going on? Why would I get an error with the example code?</p>
  
  <pre><code>library(survival)    
  aml3&lt;-survSplit(aml,cut=c(5,10,50),end="time",start="start",
              event="status",episode="i")
  </code></pre>
  
  <p>FYI: currently running R version 3.3.1 (2016-06-21)</p>
  
  <p>Update for future reference: the correct code should be</p>
  
  <pre><code>f12.split &lt;- survSplit(Surv(next.ivl,event)~.,f12, 
                   cut = cutpoints.l,
                  event = "event",
                  start = "enter", 
                   end = "next.ivl",
                   episode = "ivl")
  </code></pre>