and <code>$scale</code> for the columns
corresponding to <code>ind.col</code>, to scale each of their elements such as followed:
$$\frac{X_{i,j} - center_j}{scale_j}.$$ Default doesn't use any scaling.
You can also provide your own <code>center</code> and <code>scale</code> by using <code><a href="as_scaling_fun.html">as_scaling_fun()</a></code>.</p></dd>


<dt>ind.row</dt>
<dd><p>An optional vector of the row indices that are used.
If not specified, all rows are used. <strong>Don't use negative indices.</s