ggplot2: make the points on the line a darker color than the line color

Question

I would like to make each point on the graph a different color from the line. Here is sample data.

df <- structure(list(yrmonth = structure(c(17167, 17167, 17167, 17198, 
17198, 17198, 17226, 17226, 17226, 17257, 17257, 17257), class = "Date"), 
    index = structure(c(2L, 1L, 3L, 2L, 1L, 3L, 2L, 1L, 3L, 2L, 
    1L, 3L), .Label = c("E-W", "N-S", "OS"), class = "factor"), 
    N = c(2, 2, 1, 2, 2, 1, 2, 2, 1, 2, 2, 1), data = c(129, 
    141, 27, 150.5, 209, 87, 247.5, 243, 188, 223, 226.5, 170
    )), .Names = c("yrmonth", "index", "N", "data"), row.names = 31:42, class = "data.frame")

Here is my code for the plot.

df$yrmonth <- lubridate::ymd(df$yrmonth)

ggplot(df, aes(x=yrmonth,y=data,colour=factor(index), group=index)) + 
  geom_line(size=.4) + 
  geom_point(size=1)

I would like the green dots to be a darker green, the orange dots to be a darker orange and so forth.

Answer 1

You could use a filled point marker (shapes 21 through 25), which would allow you to set the fill colors for the points separately from the colors of the lines. In the code below, I use the same hues (the h argument to the hcl function) for the points and lines, but a lower luminance (the l argument to hcl) for the points so that they will be darker than the lines. I've also increased the line and point sizes to make it easier to see the difference.

ggplot(df, aes(x=yrmonth,y=data)) + 
  geom_line(size=1, aes(colour=factor(index))) + 
  geom_point(size=3, aes(fill=factor(index)), shape=21, colour="#FFFFFF00") +
  scale_colour_manual(values=hcl(seq(15,375,length=4)[1:3], 100, 70)) +
  scale_fill_manual(values=hcl(seq(15,375,length=4)[1:3], 100, 40)) +
  theme_classic() +
  labs(colour="Index", fill="Index")