Left join using data.table
<p>Suppose I have two <em>data.table</em>'s:</p>

<p>A:</p>

<pre><code>  A  B
1: 1 12
2: 2 13
3: 3 14
4: 4 15
</code></pre>

<p>B:</p>

<pre><code>   A  B
1: 2 13
2: 3 14
</code></pre>

<p>and I have the following code: </p>

<pre><code>merge_test = merge(dataA, dataB, by="A", all.data=TRUE)
</code></pre>

<p>I get:</p>

<pre><code>   A B.x B.y
1: 2  13  13
2: 3  14  14
</code></pre>

<p>However, I want all the rows in dataA in the final merged table. Is there a way to do this?</p>