 column type and function (or function name) as custom_column_generator.
Column generator has to accept argument size and return a vector of this size.
Third option is to pass an expression that involves existing columns. This can be a simple one,
or a call of an existing function.</p></dd>
<dt>size</dt>
<dd><p>integer, number of rows to generate.</p></dd>
</dl></div>
    <div id="value">
    <h2>Value</h2>
    <p>data.frame</p>
    </div>

    <div id="ref-examples">
    <h2>Examples</h2>
    <div class="s