Connect observations, ordered by x value.

Usage

geom_line(mapping = NULL, data = NULL, stat = "identity", position = "identity", 
  ...)

Arguments

mapping

The aesthetic mapping, usually constructed with aes or aes_string. Only needs to be set at the layer level if you are overriding the plot defaults.

data

A layer specific dataset - only needed if you want to override the plot defaults.

stat

The statistical transformation to use on the data for this layer.

position

The position adjustment to use for overlappling points on this layer

...

other arguments passed on to layer. This can include aesthetics whose values you want to set, not map. See layer for more details.

Examples

# Summarise number of movie ratings by year of movie
mry <- do.call(rbind, by(movies, round(movies$rating), function(df) {
  nums <- tapply(df$length, df$year, length)
  data.frame(rating=round(df$rating[1]), year = as.numeric(names(nums)), number=as.vector(nums))
}))

p <- ggplot(mry, aes(x=year, y=number, group=rating))
p + geom_line()



# Add aesthetic mappings
p + geom_line(aes(size = rating))


p + geom_line(aes(colour = rating))



# Change scale
p + geom_line(aes(colour = rating)) + scale_colour_gradient(low="red")


p + geom_line(aes(size = rating)) + scale_size(range = c(0.1, 3))



# Set aesthetics to fixed value
p + geom_line(colour = "red", size = 1)



# Use qplot instead
qplot(year, number, data=mry, group=rating, geom="line")



# Using a time series
qplot(date, pop, data=economics, geom="line")


qplot(date, pop, data=economics, geom="line", log="y")


qplot(date, pop, data=subset(economics, date > as.Date("2006-1-1")), geom="line")


qplot(date, pop, data=economics, size=unemploy/pop, geom="line")



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


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



# See scale_date for examples of plotting multiple times series on
# a single graph

# A simple pcp example

y2005 <- runif(300, 20, 120)
y2010 <- y2005 * runif(300, -1.05, 1.5)
group <- rep(LETTERS[1:3], each = 100)

df <- data.frame(id = seq_along(group), group, y2005, y2010)
library(reshape2) # for melt
dfm <- melt(df, id.var = c("id", "group"))
ggplot(dfm, aes(variable, value, group = id, colour = group)) +
  geom_path(alpha = 0.5)

See also