title: Query on how to make world heat map using ggplot in R?
body: <p>I want to make a world heat map of a particular disease. The dataset contains the list of countries, latitude, longitude and cases in each country. The data is available <a href="https://drive.google.com/file/d/1_EqMEZFHlujsg40gzEo83dN1zY9d9gAJ/view?usp=sharing" rel="nofollow noreferrer">here</a>. I want to represent it using a world heat map i.e. countries which have higher cases should have a darker color and it should lighten with the countries having lesser number of cases. 
  I have used ggplot and geom_map to create the same. Code is as shown below:</p>
  
  <pre><code>library(maps)
  library(plyr)
  library(gridExtra)
  
  h2 &lt;- read_excel("mapdata1.xlsx")
  
  world_map &lt;- map_data("world")
  world_map &lt;- subset(world_map, region!="Antarctica")
  
  gg &lt;- ggplot(h2)
  gg &lt;- gg + geom_map(dat=world_map, map = world_map, aes(map_id=region), 
                      fill="white", color="#7f7f7f", size=0.25)
  gg &lt;- gg + geom_map(map = world_map, aes(map_id = Country, fill = Cases), size=0.25)
  gg &lt;- gg + scale_fill_gradient(low="#fff7bc", high="#cc4c02", name="Total Cases")
  gg &lt;- gg + expand_limits(x = world_map$long, y = world_map$lat)
  gg &lt;- gg + labs(x="", y="", title="World Hotspots")
  gg &lt;- gg + theme(panel.grid=element_blank(), panel.border=element_blank())
  gg &lt;- gg + theme(axis.ticks=element_blank(), axis.text=element_blank())
  gg &lt;- gg + theme(legend.position="top")
  gg
  </code></pre>
  
  <p>When I run the code, it shows the heat map but certain countries like USA are white in color even though it has higher number of cases. I am not able to figure out why so?</p>