title: how to plot multiple plots on ggplots with lapply
body: <pre><code>library(ggplot2)
  x&lt;-c(1,2,3,4,5)
  a&lt;-c(3,8,4,7,6)
  b&lt;-c(2,9,4,8,5)
  
  df1 &lt;- data.frame(x, a, b)
  
  x&lt;-c(1,2,3,4,5)
  a&lt;-c(6,5,9,4,1)
  b&lt;-c(9,5,8,6,2)
  
  df2 &lt;- data.frame(x, a, b)
  
  df.lst &lt;- list(df1, df2)
  
  plotdata &lt;- function(x) {
    ggplot(data = x, aes(x=x, y=a, color="blue")) + 
      geom_point() +
      geom_line()
  }
  
  lapply(df.lst, plotdata)
  </code></pre>
  
  <p>I have a list of data frames and i am trying to plot the same columns on the same ggplot.  I tried with the code above but it seems to return only one plot.</p>
  
  <p>There should be 2 ggplots.  one with the "a" column data plotted and the other with the "b" column data plotted from both data frames in the list.</p>
  
  <p>i've looked at many examples and it seems that this should work.</p>