title: R: Combine a graph layout with a ggplot2 object and a gplots object
body: <p>I want to have one figure with two plots, one of them is a ggplot2 object, and the second is a plot generated with gplots. For example combine the next two plots in a row:</p>
  
  <pre><code>library(ggplot2)
  library(gplots) #For plotmeans
  df = structure(list(age = c(14, 22, 35, 21, 88, 66, 14, 22, 35, 21),
                      values = c(22, 8, 1.9, 26.8, 32, 15.,1.9, 26.8, 32, 15.)),
                 .Names = c("age", "values"),
                 row.names = 1:10,
                 class = "data.frame")
  ggplot(df, aes(values)) + geom_histogram()
  plotmeans(df$values ~ df$age)
  </code></pre>
  
  <p>I tried <code>grid</code>, <code>gridExtra</code>, <code>par</code> and <code>layout</code> but w/o success.
  Any idea how can I do so?</p>