geom_smooth

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

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Aesthetics

The following aesthetics can be used with geom_smooth. Aesthetics are mapped to variables in the data with the aes function: geom_smooth(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	#3366FF	brewer, gradient, gradient2, gradientn, grey, hue, identity, manual
fill	grey60	brewer, gradient, gradient2, gradientn, grey, hue, identity, manual
size	0.5	identity, manual, size
linetype	1	identity, linetype, manual
weight	1
alpha	0.4

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.

Returns

This function returns a layer object.

Examples

> # See stat_smooth for examples of using built in model fitting 
> # if you need some more flexible, this example shows you how to 
> # plot the fits from any model of your choosing 
>  
> library(ggplot2) 
> qplot(wt, mpg, data=mtcars, colour=factor(cyl)) 
  
>  
> model <- lm(mpg ~ wt + factor(cyl), data=mtcars) 
> grid <- with(mtcars, expand.grid( 
+   wt = seq(min(wt), max(wt), length = 20), 
+   cyl = levels(factor(cyl)) 
+ )) 
>  
> grid$mpg <- stats::predict(model, newdata=grid) 
>  
> qplot(wt, mpg, data=mtcars, colour=factor(cyl)) + geom_line(data=grid) 
  
>  
> # or with standard errors 
>  
> err <- stats::predict(model, newdata=grid, se = TRUE) 
> grid$ucl <- err$fit + 1.96 * err$se.fit 
> grid$lcl <- err$fit - 1.96 * err$se.fit 
>  
> qplot(wt, mpg, data=mtcars, colour=factor(cyl)) + 
+   geom_smooth(aes(ymin = lcl, ymax = ucl), data=grid, stat="identity") 
  

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© Hadley Wickham 2010