Can't plot circular points in R using ggplot2

Question

After experimenting with different point sizes and shapes when plotting with ggplot2, I found that I was no longer able to plot circular points. These simple examples illustrate the problem:

# Plot 1 - square points (symbol #15) appear correctly
#
df = data.frame(x = c(1, 2, 3), y = c(4, 5, 6))
g1 <- ggplot(df, aes(x = x, y = y))
g1 <- g1 + geom_point(size = 3, shape = 15)
g1

Plot 1 output:

# Plot 2 - circular points (symbol #16) appear as diamonds
#
df = data.frame(x = c(1, 2, 3), y = c(4, 5, 6))
g1 <- ggplot(df, aes(x = x, y = y))
g1 <- g1 + geom_point(size = 3, shape = 16)
g1

Plot 2 output:

# Plot 3 - triangular points (symbol #17) appear correctly
#
df = data.frame(x = c(1, 2, 3), y = c(4, 5, 6))
g1 <- ggplot(df, aes(x = x, y = y))
g1 <- g1 + geom_point(size = 3, shape = 17)
g1

Plot 3 output:

# Plot 4 - diamond points (symbol #18) appear correctly
#
df = data.frame(x = c(1, 2, 3), y = c(4, 5, 6))
g1 <- ggplot(df, aes(x = x, y = y))
g1 <- g1 + geom_point(size = 3, shape = 18)
g1

Plot 4 output:

What do I have to do to plot circular points again? (I'm running R 3.1.3 and RStudio 0.98.1103 in Windows 7.)

Answer 1

It looks like it has to do with the limited resolution of the RStudioGD() graphics device. It becomes a non-issue by avoiding the RStudio interface:

g1 <- ggplot(df, aes(x = x, y = y))
g1 <- g1 + geom_point(size = 3)
g1

(from RStudio interface via save image)

ggsave(g1, filename = "image.png")

ggsave gives you more finely-tuned control over graphics parameters, including the height/width, dpi (for raster images, eg. png), and file format. See the ?ggsave documentation for details.

Or alternatively, bump the geom_point up to size = 4.