 vector, this string will be used as the when creating new variables of the extracted measures.</p></dd>


<dt>start_numbering</dt>
<dd><p>Numeric, set to by default 1.
Change to 0 if a pre-treatment (e.g. baseline assessment) measurement point is included in <code>extract_var_list</code>.</p></dd>


<dt>add_to_data</dt>
<dd><p>Logical, if set to <code>TRUE</code>, the extracted values are added as new variables to the input dataset.
If set to false, only the ID variable and all extracted values will be ret