title: Placing image with annotation_raster when using geom_sf in ggplot2
body: <p>I am creating a geographic map of data using ggplto2 and it's geom_sf capability.
  Ultimately, I'm will create an animation of data using gganimate.  As such, I'm hoping to keep the placement of the logo within the functions of the ggplot2 library.   </p>
  
  <p>I'd like to place a logo in the lower-left corner of the map.  When I use the annotation_raster function it's not obvious what the " location (in data coordinates) giving the horizontal location of raster" [see <a href="https://ggplot2.tidyverse.org/reference/annotation_raster.html]" rel="nofollow noreferrer">https://ggplot2.tidyverse.org/reference/annotation_raster.html]</a> should be in this case.   In the examples provided the coordinates are x &amp; y on an xy plot.   </p>
  
  <p>using xmin=-Inf and ymin=-Inf anchors the image in the lower-left corner.  What values of ymax and xmax should be used to place the image with a small size that does not impinge on the map? </p>
  
  <p>The example code is below.   </p>
  
  <pre><code>   library(urbnmapr)
     library(ggplot2)
     library(dplyr)
     library(magick)
  
     # Read the logo
     logo &lt;- image_read(path='C:\\your\\local\\directory\\myawesomelogo.PNG')
     # Obtain the polygon data for states
     states_sf   &lt;- get_urbn_map("states", sf = TRUE)
  
     # Remove AK and HI
     states_sf   &lt;- states_sf[!(states_sf$state_abbv %in% c("HI","AK")),]
  
     # create random data
     dataplot &lt;- tibble(xdata=runif(49,-1,1))
  
     # add FIPS data
     dataplot &lt;- bind_cols(dataplot, tibble(state_fips = states_sf$state_fips))
  
     # Merge the polygon data into the data data
     dataplot &lt;- left_join(states_sf, dataplot, by = "state_fips")
  
     # Plot the random data 
      dataplot  %&gt;%  
      ggplot() +
      geom_sf(mapping = aes(fill = xdata), size=0.5, color=NA) +
      coord_sf(datum = NA) +   
      labs(fill  = "Random", 
           title = 'Map of Data with a Logo') + 
      scale_fill_gradient2(low='navyblue', high='red', limits=c(-1,1)) + # Add the logo
      annotation_raster(logo, ymin = -Inf, ymax = 1, xmin = -Inf, xmax = 1) + 
      theme_bw() + 
      theme(
        panel.border = element_blank(),
        plot.title   = element_text(hjust = 0.5))
  </code></pre>
  
  <p>This results in this map.
  <a href="https://i.stack.imgur.com/1iIJ7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1iIJ7.png" alt="enter image description here"></a></p>
  
  <p>I'd like the logo to be much smaller and tucked away in the lower-left corner of the image.
  Changing the size of the image seems to have no effect. </p>
  
  <p>The "logo":
  <a href="https://i.stack.imgur.com/o48f0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o48f0.png" alt="enter image description here"></a></p>
  
  <p>Thank you for your suggestions!</p>