title: ggplot extra bar in barplot
body: <p>My data is </p>
  
  <pre><code>&gt; data
      width          variable value
  1     200   mappedEnsemblTx   110
  2     400   mappedEnsemblTx   392
  3     600   mappedEnsemblTx  1055
  4     800   mappedEnsemblTx  2615
  5    1000   mappedEnsemblTx  5201
  101   200 UnmappedEnsemblTx  3927
  102   400 UnmappedEnsemblTx  5175
  103   600 UnmappedEnsemblTx  3220
  104   800 UnmappedEnsemblTx  4856
  105  1000 UnmappedEnsemblTx  7130  
  </code></pre>
  
  <p>When I plot this, instead of two bars I can see three or probably four bars in my plot. 
  Minimal code is as below:</p>
  
  <pre><code> library(ggplot2)
  
  
  g = ggplot(dat.melt,aes(x=factor(width),y=value,fill=variable), format(scientific=FALSE)) 
  g = g + geom_bar(stat='identity',position='dodge') 
  g &lt;- g + theme_bw()
  g = g + opts(axis.text.x=theme_text(angle=-90, hjust=0, size = 16), axis.text.y=theme_text(size=16))
  g &lt;- g + opts(axis.title.x = theme_text(size=18), axis.title.y = theme_text(size=18, angle=90) )
  g = g + scale_x_discrete('Total widths of the Ensembl Transcripts') + scale_y_continuous(name = 'Count') 
  g = g + coord_cartesian(ylim = c(0,7000))
  </code></pre>
  
  <p>Thanks</p>