geom_line

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

Connect observations, in ordered by x value

This page describes geom_line, see layer and qplot for how to create a complete plot from individual components.

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Aesthetics

The following aesthetics can be used with geom_line. Aesthetics are mapped to variables in the data with the aes function: geom_line(aes(x = var)). Note that you do not need quotes around the variable name.

Scales control how the variable is mapped to the aesthetic and are listed after each aesthetic.

Aesthetic	Default	Related scales
x	required	continuous, date, datetime, discrete
y	required	continuous, date, datetime, discrete
colour	black	brewer, gradient, gradient2, gradientn, grey, hue, identity, manual
size	0.5	identity, manual, size
linetype	1	identity, linetype, manual
alpha	1

Layers are divided into groups by the group aesthetic. By default this is set to the interaction of all categorical variables present in the plot.

Parameters

Parameters control the appearance of the geom. In addition to the parameters listed below (if any), any aesthetic can be used as a parameter, in which case it will override any aesthetic mapping.

arrow: NULL

Returns

This function returns a layer object.

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(to = 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") 
  
>  
> # See scale_date for examples of plotting multiple times series on 
> # a single graph