title: Prevent geom_smooth from passing weights argument
body: <p>I am trying to pass a <code>method</code> to <code>geom_smooth</code>, that I don't think is officially supported -- <code>expectreg.ls</code> from the <a href="http://cran.r-project.org/web/packages/expectreg/vignettes/expectreg.pdf" rel="nofollow"><code>expectreg</code></a> package. As required, returned objects from <code>expectreg</code> do have a <code>predict</code> method.  </p>
  
  <p>However, I think that <code>geom_smooth</code> tries to pass a <code>weights</code> argument to the method supplied, and since expectile regression depends on an IRWLS type algorithm, I think that supplying an external <code>weights</code> argument doesn't make sense, and as such is not a formal argument of <code>expectreg.ls</code>. In any case, this fails with a:</p>
  
  <pre><code>Error in method(formula, data = data, weights = weight, ...) : 
    unused argument (weights = weight)
  </code></pre>
  
  <p>I also tried modifying the <code>expectreg.ls</code> function definition to add a dummy <code>weights</code> argument, but then <code>ggplot2</code> complains that:</p>
  
  <pre><code>Error: geom_smooth requires the following missing aesthetics: y
  </code></pre>
  
  <p>At this point, I have decided to ask for help. Is there an easy way to get <code>geom_smooth</code> to work with <code>expectreg.ls</code> without creating the predictions beforehand?</p>
  
  <hr>
  
  <p>Here is some code to test solutions on:</p>
  
  <pre><code>dfX = data.frame(x = rnorm(100), y = rnorm(100))
  ggplot(dfX, aes(x, y)) +
    geom_smooth(method = "expectreg.ls", se = FALSE, aes(color = "Expectile Regression (alpha = 0.1)"), expectiles = 0.1) 
  </code></pre>