title: In geom_sf_text, how to nudge x and y in aesthetics?
body: <p>I would like to nudge the x and y position of text in ggplot2, using sf.  The justification of text can be modified in aesthetics, which then requires nudging to be also modified similarly, but nudge_x and nudge_y can't be used in aesthetics.  </p>
  
  <p>Using sp and fortified data frames, I could modify x and y in aesthetics ( x=(x+hBump), y=(y+vBump) . I don't know if that is possible in sf.</p>
  
  <p>Here are some data:</p>
  
  <pre class="lang-r prettyprint-override"><code>Cities &lt;- read.table( text=
    "City long    lat hJust   vJust   hBump   vBump
    GrandJunction -108.550649 39.063871   1   1   -1100   -1000
    Gunnison  -106.925321 38.545825   0   1   0   -1000
    Tincup    -106.47836  38.754439   1   0   0   800",
    header=TRUE )
  </code></pre>
  
  <p>Convert to sf</p>
  
  <pre class="lang-r prettyprint-override"><code>Cities.sf &lt;- st_as_sf(
    x = Cities, 
    coords = c("long", "lat"),
    crs = "+proj=longlat +datum=WGS84"
  )
  </code></pre>
  
  <p>ggplot (the coord_sf is just so labels don't get off)</p>
  
  <pre class="lang-r prettyprint-override"><code>ggplot(Cities.sf) + 
    geom_sf() + 
    coord_sf(xlim = c(-109, -106.3), ylim = c(38.4, 39.2)) +
    geom_sf_text(aes(label = City, hjust = hJust, vjust = vJust))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/p54PV.png" rel="noreferrer"><img src="https://i.stack.imgur.com/p54PV.png" alt="enter image description here"></a></p>
  
  <p>Now if we nudge for one, the others may get messed up.
  Need aesthetic nudging!</p>
  
  <pre><code>ggplot(Cities.sf) + 
    geom_sf() + 
    coord_sf(xlim = c(-109, -106.3), ylim = c(38.4, 39.2)) +
    geom_sf_text(
      aes(label = City, hjust = hJust, vjust = vJust),
      nudge_x = 0.025, nudge_y = -0.025
    )
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/oseOY.png" rel="noreferrer"><img src="https://i.stack.imgur.com/oseOY.png" alt="enter image description here"></a>
  Side question - I guess if I transform the object to another crs
  using meters, then the nudge units have to change from degrees to meters?  That is the units that hBump and vBump are in.</p>