title: Plot data in descending order as appears in data frame
body: <p>I've been battling to order and plot a simple dataframe as a bar chart in ggplot2.  </p>
  
  <p>I want to plot the data as it appears, so that the values ('count' variable) for the corresponding categories (e.g. 'humans', 'male') are plotted from high to low. </p>
  
  <p>I've followed other threads on this site asking similar questions, but can't get this to work!</p>
  
  <pre><code>## Dataset (mesh2)
  
  #Category                   Count
  
  #Humans             62
  
  #Male               40
  
  #Female             38
  
  #Adult              37
  
  #Middle Aged            30
  
  #Liver/anatomy &amp; histology          29
  
  #Organ Size                 29
  
  #Adolescent                 28
  
  #Child              21
  
  #Liver/radiography*             20
  
  #Liver Transplantation*     20
  
  #Tomography, X-Ray Computed         20
  
  #Body Weight            18
  
  #Child, Preschool               18
  
  #Living Donors*         18
  
  #Infant             16
  
  #Aged               14
  
  #Body Surface Area              14
  
  #Regression Analysis        11
  
  #Hepatectomy            10
  
  ## read in data (mesh2) as object (mesh2)
  
  mesh2 &lt;- read.csv("mesh2.csv", header = T)
  
  ## order data by count of mesh variable
  
  mesh2$cat2 &lt;- order(mesh2$Category, mesh2$Count, decreasing=TRUE)
  
  ## Barplot created in ggplot2
  
  library(ggplot2)
  
  mesh2p &lt;- ggplot(mesh2, aes(x=cat2, y=Count)) + geom_bar (stat="identity") +     scale_x_continuous(breaks=c(1:20), labels=c("Humans", "Male", "Female", "Adult", "MAged",   "Liver anat &amp; hist", "Organ Size", "Adolescent",   "Child", "Liver radiog", "Liver Transplnt", "Tomog X-Ray Computed", "Body Weight", "Child Preschool", "Living Donors", "Infant", "Aged", "BSA", "Regression Analysis", "Hepatectomy"))+ theme (axis.text.x=element_text(angle=45, hjust=1))
  </code></pre>