title: plotting a sf object with geom_sf() with any projection other than lat-long
body: <p>I am trying to plot a polygon with geom_sf() in any projection other than lat-long.</p>
  <p>I am using the example found in the <a href="http://ggplot2.tidyverse.org/reference/ggsf.html" rel="nofollow noreferrer">manual pages for geom_sf()</a>
  Importing the dataset:</p>
  <pre><code>nc &lt;- sf::st_read(system.file(&quot;shape/nc.shp&quot;, package = &quot;sf&quot;), quiet = TRUE)
  </code></pre>
  <p>transforming from latlong into epsg:3857</p>
  <pre><code>nc_3857 &lt;- sf::st_transform(nc, &quot;+init=epsg:3857&quot;)
  </code></pre>
  <p>Finally plot with ggplot2 defining the crs of the plot:</p>
  <pre><code>ggplot() +
   geom_sf(data = nc_3857, colour = &quot;red&quot;, fill = NA) +
   coord_sf(crs=st_crs(3857))
  </code></pre>
  <p>I keep getting a map in wgs84 (i.e. epsg:4326) with lat-long axes. I want to have the axes in meters, so I need <code>ggplot</code> to plot the projected polygon. What am I doing wrong?</p>