title: Converting mouse Ensembl ID's to gene names in a data frame
body: <p>I have recently produced an unsupervised hierarchical cluster heat map using 30 different RNA-seq samples.
  The x axis is labelled as the name of each sample, and the y axis displays the 100 most variable genes presented as mouse Ensembl ID's (e.g. ENSMUSG00000020573).</p>
  <p><strong>I was just wondering if there was a way for me to replace the Ensembl ID's with gene names (e.g. Pik3cg) before I input it into the pheatmap() function.</strong></p>
  <p><strong>My input table is:</strong></p>
  <pre><code>                        WT_Animal1      WT_Animal2     WT_Animal3
  ENSMUSG00000094652      0.03463869       0.7333992     -0.29986091
  ENSMUSG00000006356     -0.64264559      -0.5609578     -0.06037522
  ENSMUSG00000019897      0.09159506      -0.1133322     -0.12974861
  ENSMUSG00000027790     -0.25124228       1.2871582     -0.92491260
  ENSMUSG00000054999     -0.58618795       1.2079283     -0.89929279
  ENSMUSG00000072573      0.16812802       0.1058453     -0.16593449 
  
  </code></pre>
  <p>I changed the column names manually using colnames(mat) &lt;- c() but I want to know how to change the row names (Ensembl ID's) using a different function so I can reproduce it in further plots.</p>
  <p>I have tried to read up on using biomaRt and other packages but can't seem to work out a way to do it.</p>
  <p>Any help would be much appreciated!</p>