title: using Blue-Orange Diverging color in a ggplot map
body: <p>I want to use Blue-Orange Diverging color gradient with my ggplot map. I have found that it is available in ggthemes as document <a href="https://jrnold.github.io/ggthemes/reference/tableau_gradient_pal.html" rel="nofollow noreferrer">here</a> but how can I include it in my code?</p>
  
  <p>Reproducible Example</p>
  
  <pre><code>library(ggplot2)
  statesMap = map_data("state")
  statesMap$num = rnorm(nrow(statesMap))
  
   ggplot(statesMap, aes(x = long, y = lat, group = group, fill = num)) + 
   geom_polygon(color = "black") + scale_fill_gradient(name = "num",low = 
   "#B8E6E6", high = "darkblue", guide = "colorbar",na.value="white")
  </code></pre>
  
  <p>The code above gives the map below but I want to create similar to the Tableau map at the bottom.</p>
  
  <p><a href="https://i.stack.imgur.com/HGbFw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HGbFw.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/BlZ23.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BlZ23.png" alt="enter image description here"></a></p>