CODEWITHSUNDEEP
rggplot2
Lancophone
Lancophone

Reputation: 310

Plotting points and lines separately in R with ggplot

I'm trying to plot 2 sets of data points and a single line in R using ggplot. The issue I'm having is with the legend. As can be seen in the attached image, the legend applies the lines to all 3 data sets even though only one of them is plotted with a line.

I have melted the data into one long frame, but this still requires me to filter the data sets for each individual call to geom_line() and geom_path().

I want to graph the melted data, plotting a line based on one data set, and points on the remaining two, with a complete legend.

Here is the sample script I wrote to produce the plot:

xseq <- 1:100
x <- rnorm(n = 100, mean = 0.5, sd = 2)
x2 <- rnorm(n = 100, mean = 1, sd = 0.5)
x.lm <- lm(formula = x ~ xseq)
x.fit <- predict(x.lm, newdata = data.frame(xseq = 1:100), type = "response", se.fit = TRUE)
my_data <- data.frame(x = xseq, ypoints = x, ylines = x.fit$fit, ypoints2 = x2)

## Now try and plot it
melted_data <- melt(data = my_data, id.vars = "x")

p <- ggplot(data = melted_data, aes(x = x, y = value, color = variable, shape = variable, linetype = variable)) +
  geom_point(data = filter(melted_data, variable == "ypoints")) +
  geom_point(data = filter(melted_data, variable == "ypoints2")) +
  geom_path(data = filter(melted_data, variable == "ylines"))

pushViewport(viewport(layout = grid.layout(1, 1))) # One on top of the other
print(p, vp = viewport(layout.pos.row = 1, layout.pos.col = 1))

Resulting plot from the sample code above

Upvotes: 4

Views: 5003

Answers (1)

Pekka
Pekka

Reputation: 2448

You can set them manually like this:

We set linetype = "solid" for the first item and "blank" for others (no line).

Similarly for first item we set no shape (NA) and for others we will set whatever shape we need (I just put 7 and 8 there for an example). See e.g. http://www.r-bloggers.com/how-to-remember-point-shape-codes-in-r/ to help you to choose correct shapes for your needs.

If you are happy with dots then you can use my_shapes = c(NA,16,16) and scale_shape_manual(...) is not needed.

my_shapes = c(NA,7,8)

ggplot(data = melted_data, aes(x = x, y = value, color=variable, shape=variable )) +
   geom_path(data = filter(melted_data, variable == "ylines") ) + 
   geom_point(data = filter(melted_data, variable %in% c("ypoints", "ypoints2"))) +
   scale_colour_manual(values =  c("red", "green", "blue"),
                       guide = guide_legend(override.aes = list(
                          linetype = c("solid", "blank","blank"),
                          shape = my_shapes))) +
   scale_shape_manual(values = my_shapes)

enter image description here

But I am very curious if there is some more automated way. Hopefully someone can post better answer.

This post relied quite heavily on this answer: ggplot2: Different legend symbols for points and lines

Upvotes: 4

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