title: "Formal argument "foo" matched by multiple arguments" - how to deal with this in R?
body: <p>Sometimes, calling a function with certain arguments results in the error message <code>formal argument "foo" matched by multiple actual arguments</code>. Is it possible to print the list of the ambiguous actual arguments?</p>
  
  <p>The reason I'm asking this is currently a problem with the <code>plot</code> function for objects of class <code>mixEM</code> (generated by <code>normalmixEM</code> from the <code>mixtools</code> package). It doesn't accept the argument <code>ylim</code> yielding the error above, but when I try to use <code>ylim2</code> (the way it works for <code>xlab2</code>, <code>main2</code>, <code>col2</code> etc.), it says <code>"ylim2" is not a graphical parameter</code>. So I wonder what are the actual arguments that are matched by <code>ylim</code>?</p>
  
  <p>Using <code>formals(plot.mixEM)</code> doesn't help because it doesn't contain anything starting with <code>ylim</code>, but then at the end it refers to <code>...</code> which are the graphical parameters passed to <code>plot</code>. However, for the <code>plot</code> function, <code>ylim</code> would be unambiguous. Getting a more exact error description from <code>R</code> with a list of the conflicting arguments would be helpful.</p>
  
  <p>UPD: MWE:</p>
  
  <pre><code>library(mixtools)
  wait = faithful$waiting
  mixmdl = normalmixEM(wait)
  plot(mixmdl, which = 2, xlim = c(25, 110), nclass=20)
  lines(density(wait), lty = 2, lwd = 2)
  </code></pre>
  
  <p>This produces an error:</p>
  
  <pre><code>plot(mixmdl, which = 2, xlim = c(25, 110), ylim = c(0, .5), nclass=20)
  
  # Error in hist.default(x, prob = TRUE, main = main2, xlab = xlab2, ylim = c(0, :
  # formal argument "ylim" matched by multiple actual arguments`
  </code></pre>
  
  <p>This simply doesn't work:</p>
  
  <pre><code>plot(mixmdl, which = 2, xlim = c(25, 110), ylim2 = c(0, .5), nclass=20)
  
  # Warning messages:
  # 1: In title(main = main, sub = sub, xlab = xlab, ylab = ylab, ...) :
  #   "ylim2" is not a graphical parameter
  # 2: In axis(1, ...) : "ylim2" is not a graphical parameter
  # 3: In axis(2, ...) : "ylim2" is not a graphical parameter
  </code></pre>