title: Points changing sizes on ggplot geom_point and no legend?
body: <p>Okay so here is my code for a base map:</p>
  
  <pre><code>gg &lt;- ggmap(Peru) +
    geom_map(data = peru.coast, map = peru.coast, aes(x = long, y = lat, map_id = region),
             fill="gray", color="black") +
    xlim(-86, -70) +
    ylim(-20, -4) + 
    labs(x = "Longitude", y = "Latitude") +
    coord_map()
  </code></pre>
  
  <p>I then add in towns I wish to name manually (wasn't sure how to do it using google maps as I only wanted these 4)</p>
  
  <pre><code>gg &lt;- gg + geom_point(aes(x=-78.981885, y=-8.229354, size=3)) +
    annotate("text", label='Salaverry', size=4, x=-77.2, y=-8.229354) +
    geom_point(aes(x=-71.345838, y=-17.644347, size=3)) +
    annotate("text", x=-70.545838, y=-17.644347, label = 'Ilo', size=4) +
    geom_point(aes(x=-77.142375, y=-12.047544, size=3)) +
    annotate("text", x=-75.9, y=-12.047544, label = 'Callao', size=4) +
    geom_point(aes(x=-78.610677, y=-9.074166, size=3)) +
    annotate("text", x=-76.9, y=-9.074166, label = 'Chimbote', size=4)
  gg &lt;- gg + guides(size=FALSE) #this removes the legend with the black dot and '3' on it 
  gg
  </code></pre>
  
  <p>I get this lovely map:
  <img src="https://i.stack.imgur.com/JZHFZ.png" alt="enter image description here"></p>
  
  <p>I then use this dataset to add datapoints, and I wish to make the points bigger or smaller according to 'n' abundance</p>
  
  <pre><code>Trip_Set sex        Set.Lon     Set.Lat     n
  119_1    hembra -81.09390   -9.32338    2
  119_7    hembra -81.03117   -9.09622    1
  161_3    macho  -83.76533   -9.74533    5
  193_8    hembra -81.00888   -9.00950    7
  255_5    macho  -80.14992   -8.64592    1
  271_6    hembra -72.20233   -18.05117   6
  271_6    macho  -72.20233   -18.05117   7
  328_7    hembra -78.66667   -12.91700   2
  403_3    hembra -80.03037   -10.03900   1
  428_2    hembra -83.01305   -8.74883    2
  655_4    hembra -71.58363   -18.24882   1
  </code></pre>
  
  <p>using this code:</p>
  
  <pre><code>ggAB &lt;- gg + geom_point(data=dframe4, aes(Set.Lon, Set.Lat, colour='red', size=n)) 
  ggAB &lt;- ggAB + theme(legend.title = element_text(colour="black", size=12, face="bold")) 
  ggAB &lt;- ggAB +  guides(colour=FALSE) #This removes the legend for the red colour
  ggAB &lt;- ggAB +  scale_size(name='Sharks per line', range = c(5,9)) 
  ggAB &lt;- ggAB +  theme(legend.key=element_rect(fill = NA)) #This removes the boxes around the points 
  ggAB
  </code></pre>
  
  <p>However, when I do this... I get this: 
  <img src="https://i.stack.imgur.com/jJw4D.png" alt="enter image description here"></p>
  
  <p>The datapoints are plotted great (phew!), but why does it make the points bigger for my town names? I can't seem to get it to just keep the abundance for my 'n' number datapoints... It also doesn't put an automatic legend on (as ggplot usually does), even when I try and put one in manually using the scale_discrete function. </p>
  
  <p>I thought it might be something to do with the fact that I use <code>gg + guides(size=FALSE)</code> in the first part, but even when taking that out it doesn't work, but adds in an annoying legend for my town datapoints.</p>
  
  <p>Any ideas?</p>