kw'>&lt;-</span> <span class='no'>nlsySample</span>[<span class='no'>nlsySample</span>$<span class='no'>ID</span> <span class='kw'>%in%</span> <span class='fu'><a href='https://www.rdocumentation.org/packages/base/topics/sample'>sample</a></span>(<span class='fu'><a href='https://www.rdocumentation.org/packages/base/topics/unique'>unique</a></span>(<span class='no'>nlsySample</span>$<span class='no'>ID</span>), <span class='fl'>400</span>),]
<span class='no'>splitForm</span> <span class='kw'>&lt;-</span>~<s