title: Volcano Plot in R
body: <p>I have this line of code :</p>
  
  <pre><code>plot(gene_list$logFC, -log10(gene_list$P.Value),xlim=c(-10, 10), ylim=c(0, 15),xlab="log2 fold change", ylab="-log10 p-value")
  </code></pre>
  
  <p>which results in a volcano plot; however I want to find a way where I can color in red the points >log(2) and 
  
  <p>Edit:
  Okay so as an example I'm trying to do the following to get a volcano plot:</p>
  
  <pre><code>install.packages("ggplot2")
  </code></pre>
  
  <p>and then</p>
  
  <pre><code>gene_list &lt;- read.table("/Users/Javi/Desktop/gene_list.csv", header=T, sep=",")
  
  require(ggplot2)
  ##Highlight genes that have an absolute fold change &gt; 2 and a p-value &lt;    0.05
  gene_list$threshold = as.factor(abs(gene_list$logFC) &gt; 2 &amp; gene_list$P.Value &lt; 0.05)
  </code></pre>
  
  <h2>Construct the plot object</h2>
  
  <pre><code>g = ggplot(data=gene_list, aes(x=logFC, y=-log10(P.Value),  colour=my_palette)) +
  geom_point(alpha=0.4, size=5) +
  theme(legend.position = "none") +
  xlim(c(-10, 10)) + ylim(c(0, 15)) +
  xlab("log2 fold change") + ylab("-log10 p-value")
  </code></pre>
  
  <p>What I want to do is to color the logFC values > 2 and in blue the logFC values &lt; -2</p>