title: Merging two matrices of different size in R
body: <p>I've seen a few questions asked about this, but I wasn't able to understand any of the answers and they all seem to be closed threads.</p>
  
  <p>What I'm looking to do is to merge two matrices which have one common column but the other columns are different and the row number is significantly different. I should merge the two matrices in one by checking if any row has a matching column value of the common column.</p>
  
  <p>For example: Matrix 1</p>
  
  <pre><code>Matrix 1
  Col1 Col2 Col3 Col4
  a     b    c    d
  e     f    g    h
  i     j    k    l
  
  Matrix 2
  Col1 Col5
  a    e
  g    f
  </code></pre>
  
  <p>In the above example, the first row in Matrices 1 and two have the same entries in Col1 and Col3, while rows 2 and 3 are dissimilar.</p>
  
  <p>I would like the output to look as follows:</p>
  
  <pre><code>NewMatrix
  Col1 Col2 Col3 Col4 Col5
  a     b   c    d    e
  e     f   g    h    NA
  i     j   k    l    NA
  g     NA  NA    NA   f
  </code></pre>
  
  <p>So that the matching rows are joined, while any rows that don't match are simply added on to the end.</p>
  
  <p>Would anyone have an idea of how to do this?</p>