\BeginKnitrBlock{rmdnote}<div class="rmdnote">Note the empty argument --- denoted with `, ,` --- in the preceding code chunk is included to highlight `op`, the third argument in `[` for `sf` objects.
One can use this to change the subsetting operation in many ways.
`nz_height[canterbury, 2, op = st_disjoint]`, for example, returns the same rows but only includes the second attribute column (see `` sf:::`[.sf` `` and the `?sf` for details).</div>\EndKnitrBlock{rmdnote}