Creating repeating set from another column in R : <p>Using these dataset:</p>

<pre><code>[A]
100
200
300

[B]
A
B
C
</code></pre>

<p>I would like to make this column:</p>

<pre><code>[A]   [B]
100    A
100    B
100    C
200    A
200    B
200    C
300    A
300    B
300    C
</code></pre>

<p>I would like to use rep function in R, but it does not work.
How do I create this column? </p>
