title: How to order points in a ggplot based on a variable I specify
body: <p>I have a plot of Proportion vs Names. Im trying to order a ggplot by the Proportions but even though I order the dataframe, the plot wants to order things alphabetically according to the x-axis values. How do I order by the y axis values instead</p>
  
  <pre><code>resultOrder &lt;- result[order(result$Proportion), ]
  
  ggplot() + 
  geom_point(aes(resultOrder$Names, resultOrder$Proportion), resultOrder) +  
  geom_point(shape=1) +
  labs(title="Number of SVs each repeat element is found in (as a percentage,     filtered for &gt;20%)", x="TY [°C]", y="Txxx") +
  #geom_point(aes(mergedGroup4$Rptname, mergedGroup4$PercentageChangeForWholeSV),mergedGroup4) + theme(axis.text.x=element_text(angle=-90)) + 
  xlab("Repetitive elements") + 
  ylab("Percentage of SVs") +
  theme(axis.text.x=element_text(angle=-90)) +
  theme(legend.position="top")
  </code></pre>
  
  <p>Sample data</p>
  
  <pre><code>                          Names Values Proportion
   FLAM_C                   FLAM_C   1112   20.03965
   MER112                   MER112   1115   20.09371
   L1MA10                   L1MA10   1116   20.11173
   L1PB3                     L1PB3   1121   20.20184
   LTR78B                   LTR78B   1125   20.27392
   MLT1H1                   MLT1H1   1126   20.29194
   (TG)n                     (TG)n   1127   20.30997
   Charlie7               Charlie7   1129   20.34601
   MamRep605             MamRep605   1133   20.41809
   LTR16A                   LTR16A   1136   20.47216
   Charlie1b             Charlie1b   1139   20.52622
   L1PA6                     L1PA6   1142   20.58028
   MLT1G1                   MLT1G1   1148   20.68841
   LTR67B                   LTR67B   1150   20.72445
   MER58A                   MER58A   1162   20.94071
  </code></pre>