title: "promise already under evaluation" error in R caret's rfe function
body: <p>I have a matrix <code>X</code> and vector <code>Y</code> which I use as arguments into the <code>rfe</code> function from the <code>caret</code> package. It's as simple as:</p>
  
  <p>I get a weird error which I can't decipher:</p>
  
  <blockquote>
    <p>promise already under evaluation: recursive default argument reference or earlier problems?</p>
  </blockquote>
  
  <p>EDIT:
  Here is a reproducible example for the first 5 rows of my data:</p>
  
  <pre><code>library(caret)
  
  X_values = c(29.04,96.57,4.57,94.23,66.81,26.71,69.01,77.06,49.52,97.59,47.57,64.07,24.25,11.27,77.30,90.99,44.05,30.96,96.32,16.04)
  X = matrix(X_values, nrow = 5, ncol=4)
  Y = c(5608.11,2916.61,5093.05,3949.35,2482.52)
  
  rfe(X, Y)
  </code></pre>
  
  <p>My R version is 3.2.3. Caret package is 6.0-76.</p>
  
  <p>Does anybody know what this is?</p>