title: How to set data for R survival analysis
body: <p>I'm sorry if the question looks silly, but I have a small data set which I would like to manipulate with function "survfit" of R package "survival", and, well, I don't know to set a proper dataframe usable by "survfit"; data are as follows:</p>
  
  <pre><code>      time number_at_risk number_death number_censored
      1   25             10            0               2
      2   28              8            1               0
      3   33              7            1               0
      4   37              6            0               1
      5   41              5            1               0
      6   43              4            0               1
      7   48              3            0               3
  </code></pre>
  
  <p>And now, if I run the usual syntax <code>survfit(Surv(time, number_censored) ~ 1, data = data)</code>, it gives me the warning <code>In Surv(time, number_censored) : Invalid status value, converted to NA</code>.</p>
  
  <p>Obviously, the data are not properly organized. So, how should I set my dataframe?
  Thanks.</p>