Connect observations.


geom_path(mapping = NULL, data = NULL, stat = "identity", position = "identity", lineend = "butt", linejoin = "round", linemitre = 1, na.rm = FALSE, arrow = NULL, show.legend = NA, inherit.aes = TRUE, ...)
geom_line(mapping = NULL, data = NULL, stat = "identity", position = "identity", na.rm = FALSE, show.legend = NA, inherit.aes = TRUE, ...)
geom_step(mapping = NULL, data = NULL, stat = "identity", position = "identity", direction = "hv", na.rm = FALSE, show.legend = NA, inherit.aes = TRUE, ...)


Set of aesthetic mappings created by aes or aes_. If specified and inherit.aes = TRUE (the default), is combined with the default mapping at the top level of the plot. You only need to supply mapping if there isn't a mapping defined for the plot.
A data frame. If specified, overrides the default data frame defined at the top level of the plot.
The statistical transformation to use on the data for this layer, as a string.
Position adjustment, either as a string, or the result of a call to a position adjustment function.
Line end style (round, butt, square)
Line join style (round, mitre, bevel)
Line mitre limit (number greater than 1)
If FALSE (the default), removes missing values with a warning. If TRUE silently removes missing values.
Arrow specification, as created by arrow
logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes.
If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders.
other arguments passed on to layer. There are three types of arguments you can use here:
  • Aesthetics: to set an aesthetic to a fixed value, like color = "red" or size = 3.
  • Other arguments to the layer, for example you override the default stat associated with the layer.
  • Other arguments passed on to the stat.
direction of stairs: 'vh' for vertical then horizontal, or 'hv' for horizontal then vertical


geom_path() connects the observations in the order in which they appear in the data. geom_line() connects them in order of the variable on the x axis. geom_step() creates a stairstep plot, highlighting exactly when changes occur.


geom_path understands the following aesthetics (required aesthetics are in bold):

  • x
  • y
  • alpha
  • colour
  • linetype
  • size


# geom_line() is suitable for time series ggplot(economics, aes(date, unemploy)) + geom_line()

ggplot(economics_long, aes(date, value01, colour = variable)) + geom_line()

# geom_step() is useful when you want to highlight exactly when # the y value chanes recent <- economics[economics$date > as.Date("2013-01-01"), ] ggplot(recent, aes(date, unemploy)) + geom_line()

ggplot(recent, aes(date, unemploy)) + geom_step()

# geom_path lets you explore how two variables are related over time, # e.g. unemployment and personal savings rate m <- ggplot(economics, aes(unemploy/pop, psavert)) m + geom_path()

m + geom_path(aes(colour = as.numeric(date)))

# Changing parameters ---------------------------------------------- ggplot(economics, aes(date, unemploy)) + geom_line(colour = "red")

# Use the arrow parameter to add an arrow to the line # See ?arrow for more details c <- ggplot(economics, aes(x = date, y = pop)) c + geom_line(arrow = arrow())

c + geom_line( arrow = arrow(angle = 15, ends = "both", type = "closed") )

# Control line join parameters df <- data.frame(x = 1:3, y = c(4, 1, 9)) base <- ggplot(df, aes(x, y)) base + geom_path(size = 10)

base + geom_path(size = 10, lineend = "round")

base + geom_path(size = 10, linejoin = "mitre", lineend = "butt")

# NAs break the line. Use na.rm = T to suppress the warning message df <- data.frame( x = 1:5, y1 = c(1, 2, 3, 4, NA), y2 = c(NA, 2, 3, 4, 5), y3 = c(1, 2, NA, 4, 5) ) ggplot(df, aes(x, y1)) + geom_point() + geom_line()
Warning message: Removed 1 rows containing missing values (geom_point). Warning message: Removed 1 rows containing missing values (geom_path).

ggplot(df, aes(x, y2)) + geom_point() + geom_line()
Warning message: Removed 1 rows containing missing values (geom_point). Warning message: Removed 1 rows containing missing values (geom_path).

ggplot(df, aes(x, y3)) + geom_point() + geom_line()
Warning message: Removed 1 rows containing missing values (geom_point).

# Setting line type vs colour/size # Line type needs to be applied to a line as a whole, so it can # not be used with colour or size that vary across a line x <- seq(0.01, .99, length.out = 100) df <- data.frame( x = rep(x, 2), y = c(qlogis(x), 2 * qlogis(x)), group = rep(c("a","b"), each = 100) ) p <- ggplot(df, aes(x=x, y=y, group=group)) # These work p + geom_line(linetype = 2)

p + geom_line(aes(colour = group), linetype = 2)

p + geom_line(aes(colour = x))

# But this doesn't should_stop(p + geom_line(aes(colour = x), linetype=2))

See also

geom_polygon: Filled paths (polygons); geom_segment: Line segments