e>attribute = ~ expression</code>.</p>
<p>In formulas of the form <code>A | B</code>, <code>B</code> will be used to form facets using
<code><a href="https://ggplot2.tidyverse.org/reference/facet_wrap.html" class="external-link">ggplot2::facet_wrap()</a></code> or <code><a href="https://ggplot2.tidyverse.org/reference/facet_grid.html" class="external-link">ggplot2::facet_grid()</a></code>.
This provides an alternative to
<code><a href="gf_facet_grid.html">gf_facet_wrap()</a></code> and
<code><a href="gf_fac