title: Changing x axis label in GGPlot2
body: <p>I have an r data set which has money spendings spread across months, and also grouped by years.</p>
  
  <pre><code>Year|Mth_Year|Mth_Spend
  2004|01-2004|42507163
  2004|02-2004|3377592
  2006|10-2006|3507636
  2006|11-2006|4479139
  2006|12-2006|2439603
  </code></pre>
  
  <p>I need to display the monthly information (grouped year wise), so that some quick comparisons can be done.</p>
  
  <p>I am using the ggplot, geom_bar options to display the monthly spends. Below is the code, I use.</p>
  
  <pre><code>ggplot(data=yearly_spending,aes(x=Year,y=Mth_Spend,fill=Mth_Year))+
    geom_bar(stat="identity",color="black",position=position_dodge())+
    theme(axis.text.x=element_text(angle=90,hjust=1))
  </code></pre>
  
  <p>When I use this code, the bar chart is getting displayed. But in X Axis, only the years (2004, 2005 &amp; 2006) are displayed. Can I get the months also displayed above the years. The years can appear horizontally, and while months can be placed vertically. </p>