>
<dd><p>the month of birth</p></dd>

<dt><code>birthyear</code></dt>
<dd><p>the year of birth</p></dd>

<dt><code>length</code></dt>
<dd><p>length of longer foot (in cm)</p></dd>

<dt><code>width</code></dt>
<dd><p>width of longer foot (in cm)</p></dd>

<dt><code>sex</code></dt>
<dd><p>a factor with levels <code>B</code> <code>G</code></p></dd>

<dt><code>biggerfoot</code></dt>
<dd><p>a factor with levels <code>L</code> <code>R</code></p></dd>

<dt><code>domhand</code></dt>
<dd><p>a factor with levels <cod