stat_quantile

stat_quantile(mapping=NULL, data=NULL, geom="quantile", position="identity", quantiles=c(0.25, 0.5, 0.75), formula=y ~ x, method="rq", na.rm=FALSE, ...)

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Aesthetics

The following aesthetics can be used with stat_quantile. Aesthetics are mapped to variables in the data with the aes function: stat_quantile(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
group	..quantile..

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.

New variables produced by the statistic

To use these variables in an aesthetic mapping, you need to surrond them with .., like aes(x = ..output..). This tells ggplot that the variable isn't the original dataset, but has been created by the statistic.

• quantile, quantile of distribution

Parameters

Parameters control the appearance of the stat. 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.

• quantiles: conditional quantiles of y to calculate and display
• formula: formula relating y variables to x variables
• xseq: exact points to evaluate smooth at, overrides n
• method: NULL
• na.rm: NULL
• ...: other arguments

Returns

This function returns a layer object.

Examples

> msamp <- movies[sample(nrow(movies), 1000), ] 
> m <- ggplot(msamp, aes(y=rating, x=year)) + geom_point() 
> m + stat_quantile() 
  
> m + stat_quantile(quantiles = 0.5) 
  
> m + stat_quantile(quantiles = seq(0.1, 0.9, by=0.1)) 
Warning: Solution may be nonunique
  
>  
> # Doesn't work.  Not sure why. 
> # m + stat_quantile(method = rqss, formula = y ~ qss(x), quantiles = 0.5) 
>  
> # Add aesthetic mappings 
> m + stat_quantile(aes(weight=votes)) 
  
>  
> # Change scale 
> m + stat_quantile(aes(colour = ..quantile..), quantiles = seq(0.05, 0.95, by=0. 
+ 05)) 
Warning: Solution may be nonunique
  
> m + stat_quantile(aes(colour = ..quantile..), quantiles = seq(0.05, 0.95, by=0. 
+ 05)) + 
+   scale_colour_gradient2(midpoint=0.5, low="green", mid="yellow", high="green") 
Warning: Solution may be nonunique
  
>  
> # Set aesthetics to fixed value 
> m + stat_quantile(colour="red", size=2, linetype=2) 
  
>  
> # Use qplot instead 
> qplot(year, rating, data=movies, geom="quantile") 
  

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© Hadley Wickham 2010