title: How do I change the projection method used by R for mapping coordinates?
body: <p>My question is very similar to this one:
  <a href="https://stackoverflow.com/questions/11164974/r-plot-filled-longitude-latitude-grid-cells-on-map">R Plot Filled Longitude-Latitude Grid Cells on Map</a></p>
  
  <p>I used the solution given by Richard to plot the number of earthquakes over a certain time period onto a map of California</p>
  
  <pre><code>library(ggplot2)
  library(maps)
  caliMap &lt;- map_data('state','california',lwd=50)
  g &lt;- (ggplot(aes(x=Longitude,y=Latitude,fill=Events),data=eqGrid) + 
       geom_tile()) + 
       geom_polygon(data=caliMap,aes(x=long, y=lat, group=group), 
                    colour='firebrick', fill='white', alpha=0, lwd=1.2)
  </code></pre>
  
  <p>This is a modified code from Richard's given solution. My question is, does this take into account the alteration of the geometry from the projection of a sphere onto a plane? If so I have difficulty seeing where this is being done. How can I change the form of projection used?</p>
  
  <p>Also, as an aside, how can I change the titles of my legend, etc.? From what I see, if I change the titles, it won't properly pull them from the titles of my data.frame (I really need to change the legend to say 'Events (log n)', but I can't figure it out, and putting a space anywhere messes things up). </p>
  
  <p>I just started using R today after seeing that it had a seemingly easy solution to a problem I couldn't find much help for elsewhere. I'm not a very experienced programmer either, so I appreciate if you can be as simple as possible. </p>