title: ggplot invalid argument to unary operator
body: <p>I am getting the below error msg when running ggplot pie chart...any idea what issue could be?</p>
  
  <p>code is :</p>
  
  <pre><code>ggplot(pie_unrated, aes(x = "FEBRUARY IBG UNRATED Book COMPOSITION", y = prop, 
  fill = ProductDetails)) + geom_bar(width = 1, 
  stat = "identity", color = "white") 
  + coord_polar(theta = "y", start = 0) + ggpubr::fill_palette("jco") 
  +theme_void()
  </code></pre>
  
  <p>My error Msg : </p>
  
  <pre><code> Error in +coord_polar(theta = "y", start = 0) : 
      invalid argument to unary operator
  </code></pre>
  
  <p>></p>
  
  <pre><code> dput(head(pie_unrated)
  structure(list(RatingStatus = c("UNRATED", "UNRATED", "UNRATED", 
  "UNRATED", "UNRATED", "UNRATED"), ProductDetails = structure(c(1L, 
  2L, 6L, 7L, 9L, 10L), .Label = c("ACB", "Bonds", "Cash and Short Term", 
  "Deposit with Banks", "LBD", "LC", "LG", "loan", "Loan", "OD", 
  "Treasury Bonds"), class = "factor"), counts = c(10L, 1L, 21L, 
  102L, 758L, 126L), prop = c(1, 0.1, 2.1, 10, 74.5, 12.4), lab.ybos = c(0.5, 
  1.05, 2.15, 8.2, 50.45, 93.9)), .Names = c("RatingStatus", "ProductDetails", 
  "counts", "prop", "lab.ybos"), row.names = c(NA, -6L), class = c("grouped_df", 
  "tbl_df", "tbl", "data.frame"), vars = "RatingStatus", drop = TRUE, indices = list(
      0:5), group_sizes = 6L, biggest_group_size = 6L, labels = structure(list(
      RatingStatus = "UNRATED"), row.names = c(NA, -1L), class = "data.frame", vars = "RatingStatus", drop = TRUE, .Names = "RatingStatus"))
  </code></pre>