geom_hline with factor as yintercept

[Matt Neilson]

Hi all,

I've run into a problem as I'm testing some of my code with the transition from 0.8.9 to 0.9.0. I am trying to make a Cleveland style dotplot with horizontal lines to act as guides (e.g., like panel.grid.major but only on y axis). In 0.8.9, this code generally worked to produce the desired result:

## test dataset
test <- data.frame(Level = c("first", "Second", "third", "Fourth"),
                   x1 = c(100, 200, 300, 400),
                   x2 = c(300, 145, 185, 227)
                   )
## dotchart
ggplot(test, aes(x = x1, y = reorder(Level, x2))) +
  geom_hline(aes(yintercept = reorder(Level, x2)), color = "grey50", size = 0.25, alpha = 0.5) +
  geom_point(size = 4) +
  geom_text(aes(label = x1), vjust = -1) +
  theme_bw() +
  opts(title = "test",
       panel.background = theme_rect(linetype = "solid", size = 1),
       panel.grid.minor = theme_blank(),
       panel.grid.major = theme_blank()
       )

The resultant plot was a dot chart in b/w with faint grey horizontal lines as guides. With 0.9.0, I cannot successfully generate this same plot. I've tried several different versions, but to no avail:

> ggplot(test, aes(x = x1, y = reorder(Level, x2))) +
+   geom_hline(aes(yintercept = reorder(Level, x2)), color = "grey50", size = 0.25, alpha = 0.5) +
+   geom_point(size = 4) +
+   geom_text(aes(label = x1), vjust = -1) +
+   theme_bw() +
+   opts(title = "test",
+        panel.background = theme_rect(linetype = "solid", size = 1),
+        panel.grid.minor = theme_blank(),
+        panel.grid.major = theme_blank()
+        )
Error in x - from[1] : non-numeric argument to binary operator

> ggplot(test, aes(x = x1, y = reorder(Level, x2))) +
+   geom_hline(yintercept = reorder(Level, x2), color = "grey50", size = 0.25, alpha = 0.5) +
+   geom_point(size = 4) +
+   geom_text(aes(label = x1), vjust = -1) +
+   theme_bw() +
+   opts(title = "test",
+        panel.background = theme_rect(linetype = "solid", size = 1),
+        panel.grid.minor = theme_blank(),
+        panel.grid.major = theme_blank()
+        )
Error in reorder(Level, x2) : object 'Level' not found
> ggplot(test, aes(x = x1, y = reorder(Level, x2))) +
+   geom_hline(yintercept = Level, color = "grey50", size = 0.25, alpha = 0.5) +
+   geom_point(size = 4) +
+   geom_text(aes(label = x1), vjust = -1) +
+   theme_bw() +
+   opts(title = "test",
+        panel.background = theme_rect(linetype = "solid", size = 1),
+        panel.grid.minor = theme_blank(),
+        panel.grid.major = theme_blank()
+        )
Error in get(x, envir = this, inherits = inh)(this, ...) : 
  object 'Level' not found
> ggplot(test, aes(x = x1, y = reorder(Level, x2))) +
+   geom_hline(aes(yintercept = Level), color = "grey50", size = 0.25, alpha = 0.5) +
+   geom_point(size = 4) +
+   geom_text(aes(label = x1), vjust = -1) +
+   theme_bw() +
+   opts(title = "test",
+        panel.background = theme_rect(linetype = "solid", size = 1),
+        panel.grid.minor = theme_blank(),
+        panel.grid.major = theme_blank()
+        )
Error in x - from[1] : non-numeric argument to binary operator
> ggplot(test, aes(x = x1, y = reorder(Level, x2))) +
+   geom_hline(aes(yintercept = reorder(test$Level, test$x2)), color = "grey50", size = 0.25, alpha = 0.5) +
+   geom_point(size = 4) +
+   geom_text(aes(label = x1), vjust = -1) +
+   theme_bw() +
+   opts(title = "test",
+        panel.background = theme_rect(linetype = "solid", size = 1),
+        panel.grid.minor = theme_blank(),
+        panel.grid.major = theme_blank()
+        )
Error in x - from[1] : non-numeric argument to binary operator

Any suggestions or solutions would be greatly appreciated.

Cheers,
-Matt

[Matt Neilson]

The closest that I've come to solving this is:

> x <- print(ggplot(test, aes(x = x1, y = reorder(Level, x2))) + 
+   geom_hline(yintercept = reorder(test$Level, test$x2), color = "grey50", size = 0.25, alpha = 0.5) +

+   geom_point(size = 4) +
+   geom_text(aes(label = x1), vjust = -1) +
+   theme_bw() +
+   opts(title = "test",
+        panel.background = theme_rect(linetype = "solid", size = 1),
+        panel.grid.minor = theme_blank(),
+        panel.grid.major = theme_blank()

+        ))
Error : Invalid intercept type: should be a numeric vector, a function, or a name of a function

This allows the plot to be rendered, but is still missing all of the horizontal lines (whereas all of the other plot ggplot statements did not render at all).

[Matt Neilson]

I seem to have found a two-part solution to this:

1. Setting the y-axis as discrete before the call to geom_hline
2. forcing the factor variable to numeric using as.numeric()

Solution as follows produces the Cleveland style dot plot as desired:

test <- data.frame(Level = c("first", "Second", "third", "Fourth"),
                   x1 = c(100, 200, 300, 400),
                   x2 = c(300, 145, 185, 227)
                   )

ggplot(test, aes(x = x1, y = reorder(Level, x2))) +

  scale_y_discrete() +
  geom_hline(aes(yintercept = as.numeric(Level)), colour = "grey50", size = 0.25, alpha = 0.5) +

[Matt Neilson]

With thanks to Dennis Murphy for the as.numeric suggestion...