title: Discrete value supplied to continous scale R
body: <p>I know this question has been asked several times here . But I seem to be getting the same error message "Discrete value supplied to continuous scale" even when I think my code is good enough. I don't understand the reason. I import the longitude and latitude value from a <code>csv</code> file and construct a data frame. But I am not able to plot the points on the map all I am getting is a map of Europe with no points.</p>
  
  <pre><code>library(ggmap)
  library(ggplot2)
  
  g &lt;- data.frame(lon=longitude, lat=latitude)
  
  Europe &lt;- get_map(location="Europe", zoom=3)
  
  map &lt;- ggmap(Europe)
  map + geom_point(data=g, aes(x=longitude, y=latitude), color="blue", size=3)
  </code></pre>
  
  <p>sample data:</p>
  
  <pre><code>latitude  
  28.42222222
  29.76328
  18.079733
  19.2539846
  27.66955857
  23.1525609
  12.958251
  16.3577847
  28.5912216
  19.254039
  25.1450198
  23.15276151
  19.2539879
  19.253986
  28.6598034
  23.1530814
  
  longitude
  100.7680556
  95.36327
  73.418583
  73.1403781
  84.42628936
  79.9333897
  77.5543671
  80.8691776
  77.1237985
  73.1403918
  85.2033903
  79.9332153
  73.140418
  73.1404192
  77.1903172
  79.9329372
  </code></pre>
  
  <p>EDITED DPUT</p>
  
  <pre><code>&gt; dput(g)
  structure(list(lon = structure(c(1L, 16L, 6L, 2L, 14L, 12L, 9L, 
  13L, 7L, 3L, 15L, 11L, 4L, 5L, 8L, 10L), .Label = c("100.7680556", 
  "73.1403781", "73.1403918", "73.140418", "73.1404192", "73.418583", 
  "77.1237985", "77.1903172", "77.5543671", "79.9329372", "79.9332153", 
  "79.9333897", "80.8691776", "84.42628936", "85.2033903", "95.36327"
  ), class = "factor"), lat = structure(c(13L, 16L, 3L, 4L, 12L, 
  8L, 1L, 2L, 14L, 7L, 11L, 9L, 6L, 5L, 15L, 10L), .Label = c("12.958251", 
  "16.3577847", "18.079733", "19.2539846", "19.253986", "19.2539879", 
  "19.254039", "23.1525609", "23.15276151", "23.1530814", "25.1450198", 
  "27.66955857", "28.42222222", "28.5912216", "28.6598034", "29.76328"
  ), class = "factor")), .Names = c("lon", "lat"), row.names = c(NA, 
  -16L), class = "data.frame")
  </code></pre>