title: R: update.formula limit to 512 chars
body: <p>I am trying to "paste " together a formula to use in the mob function of party.  This means the formula will be of the form y ~ x1+ ...+xM | z1+..zN.</p>
  
  <p>I am doing some preliminary fits of y ~ x1+ ...+xM, then want to add the conditional part of the equation using update().</p>
  
  <p>Here's the test code:</p>
  
  <pre><code>var1 &lt;- 1:78
  x1 &lt;- paste("x", var1, sep="")
  f1 &lt;- paste("f", var1[1:10], sep="")                                
  
  # use first 77 variables
  fmla &lt;- as.formula( paste("y ~ ", paste(x1[1:77], collapse=" + ", sep=""), sep=""))
  fmla2 &lt;- update(fmla, paste(". ~ . | ", paste(f1, collapse= " + "), sep=""))
  
  # CHANGE x to all 78 variables
  fmla &lt;- as.formula( paste("y ~ ", paste(x1, collapse=" + ", sep=""), sep=""))
  fmla2 &lt;- update(fmla, paste(". ~ . | ", paste(f1, collapse= " + "), sep=""))
  </code></pre>
  
  <p>I have run this in Windows and Linux (64 bit) and both fail when using all 78 terms (and anything more than 78 terms).  The error message contains <strong>Error in parse(text = x) : :1:514: unexpected ')'</strong>.</p>
  
  <p>Changing the length of the names of the x variables will break the update() with fewer variables, but always with an error referring to just more than 512 characters.</p>
  
  <p>Is there a workaround to this?</p>
  
  <p>Thanks.</p>