title: Reorder label y axis in ggplot
body: <p>I am trying to have labels of the y axis from a ggplot between a categorical (species in Y) and a continuous variable (in X) presented in alphabetic order. But I am getting the Y presented with the last species in alphabetic order on the top of my Y axis and the first species in alphabetic order on the bottom.</p>
  
  <p>Since I am new I cannot show images, but it looks like a list of species on the y axis and for each species is represented a point with its standard error bars to the corresponding x value (mean). And the species are presented with Wood Duck on the top and Alpine Swift on the bottom (the middle being ordered in alphabetic order).</p>
  
  <p>I would like to have the opposite (species Alpine Swift on the top and on the bottom the species Wood Duck).</p>
  
  <p>the command I used to plot the graph is the following:</p>
  
  <pre><code># getting data for the error bars
  limits&lt;-aes(xmax=mydata$Xvalues+mydata$Xvalues_SD,
          xmin=(mydata$Xvalues-mydata$Xvalues_SD))
  
  # plot graph
  graph&lt;-ggplot(data=mydata,aes(x = Xvalues, y = species))
         +scale_y_discrete("Species")
         +scale_x_continuous(" ")+geom_point()+theme_bw()+geom_errorbarh(limits)
  </code></pre>
  
  <p>I have tried to order my data set before to upload the data and run the graph.
  I have also tried to reorder the species factor using the following command:</p>
  
  <pre><code>mydata$species &lt;- ordered(mydata$species, levels=c("Alpine Swift","Azure-winged Magpie","Barn Swallow","Black-browed Albatross","Blue Tit1","Blue Tit2","Blue-footed Booby","Collared Flycatcher","Common Barn Owl","Common Buzzard","Eurasian Sparrowhawk","European Oystercatcher","Florida Scrub-Jay","Goshawk","Great Tit","Green Woodhoopoe","Grey-headed Albatross","House Sparrow","Indigo Bunting","Lesser Snow Goose","Long-tailed Tit","Meadow Pipit","Merlin","Mute Swan","Osprey","Pied Flycatcher","Pinyon Jay","Sheychelles Warbler","Short-tailed Shearwater","Siberian Jay","Tawny Owl","Ural Owl","Wandering Albatross","Western Gull1","Western Gull2","Wood Duck"))
  </code></pre>
  
  <p>But I am getting the same graph.</p>
  
  <p>How should I do to change the order of my Y axis?</p>