title: Change order of ggplot2 bars with dates on x axis
body: <p>I have the following data and am trying to create a barplot in R with ggplot2 which have values associated with date values</p>
  
  <pre><code>conv = c(10, 4.76, 17.14, 25, 26.47, 37.5, 20.83, 25.53, 32.5, 16.7, 27.33)
  click = c(20, 42, 35, 28, 34, 48, 48, 47, 40, 30, 30)
  
  dat &lt;- data.frame(date=c("July 7", "July 8", "July 9", "July 10", "July 11", "July 12", "July 13",
                           "July 14", "July 15", "July 16", "July 17"), click=c(click), conv=c(conv))
  dat
  </code></pre>
  
  <p>However, when I run the following commands, the bars aren't in the proper order.</p>
  
  <pre><code>library(ggplot2)
  ggplot(dat, aes(date, conv)) +  geom_bar(fill="#336699") + ylim(c(0,50)) +
          opts(title="") +
          opts(axis.text.y=theme_text(family="sans", face="bold", size=10)) +
          opts(axis.text.x=theme_text(family="sans", face="bold", size=8)) +
          opts(plot.title = theme_text(size=15, face="bold")) +
          xlab("") + ylab("")
  </code></pre>
  
  <p>The variable date is properly ordered from July 7 to July 17, and don't know why ggplot2 has a  problem with this. Is there a quick function to fix this problem without having to reorder the data in the original data set.</p>