title: R ggplot2 two categorical variables in facet grid
body: <p>I have a plot with aesthetic mappings <code>(gear, hp, col = cyl) + geom_line</code> and <code>geom_point</code></p>
  
  <pre><code>data(mtcars)
  
  library(ggplot2)
  
  ggplot(mtcars, aes(as.factor(gear), hp, col = as.factor(cyl))) +
      geom_line() +
      geom_point(aes(shape = as.factor(cyl))) +
      facet_grid(cyl~.) +
      scale_color_manual(values = c("red", "black", "goldenrod"))
  </code></pre>
  
  <p>This works just fine. The problem arises when I want to manually label the legend (guide)</p>
  
  <pre><code>ggplot(mtcars, aes(as.factor(gear), hp, col = as.factor(cyl))) +
      geom_line() +
      geom_point(aes(shape = as.factor(cyl))) +
      facet_grid(cyl~.) +
      scale_color_manual(values = c("red", "black", "goldenrod"), name = "Cylinder)
  </code></pre>
  
  <p>It pulls apart the legend and splits it into two: Cylinder (with cols) and <code>as.factor(cyl)</code> for the shapes. How do I get rid of the <code>as.factor(cyl)</code> or keep the legend combined and still rename it manually? I assume I just need to shift some things around.</p>