\BeginKnitrBlock{exercise}\iffalse{-91-68-105-102-102-101-114-101-110-116-32-107-105-110-100-115-32-111-102-32-118-97-114-105-97-98-108-101-115-93-}\fi{}<div class="exercise"><span class="exercise" id="exr:unnamed-chunk-19"><strong>(\#exr:unnamed-chunk-19)  \iffalse (Different kinds of variables) \fi{} </strong></span>What different kinds of variables do you see in Table \@ref(tab:dataexcerpt)?</div>\EndKnitrBlock{exercise}