o not need to worry about reduceReductions - there is no merge step.</p></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>colname</code> - One or more column names. If multiple column names are specified then perElemFn will need to take additional arguments.</dd>
<dd><code>perElemFn</code> - A function that takes the previous context along with the current row&rsquo;s column values and returns a new context.</dd>
<dd><code>finalizeFn</code> - Optional function that performs a final 