stat_bin

stat_bin(mapping=NULL, data=NULL, geom="bar", position="stack", width=0.9, drop=FALSE, ...)

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Aesthetics

The following aesthetics can be used with stat_bin. Aesthetics are mapped to variables in the data with the aes function: stat_bin(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	..count..	continuous, date, datetime, discrete

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.

• count, number of points in bin
• density, density of points in bin, scaled to integrate to 1
• ncount, count, scaled to maximum of 1
• ndensity, density, scaled to maximum of 1

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.

• binwidth: Bin width to use. Defaults to 1/30 of the range of the data.
• origin: NULL
• breaks: Actual breaks to use. Overrides bin width
• width: Width of bars when used on categorical data
• drop: NULL
• ...: other arguments

Returns

This function returns a layer object.

Examples

> m <- ggplot(movies, aes(x=rating)) 
> m + stat_bin() 
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

  
> m + stat_bin(binwidth=0.1) 
  
> m + stat_bin(breaks=seq(4,6, by=0.1)) 
  
> # See geom_histogram for more histogram examples 
>  
> # To create a unit area histogram, use aes(y = ..density..) 
> (linehist <- m + stat_bin(aes(y = ..density..), binwidth=0.1, 
+   geom="line", position="identity")) 
  
> linehist + stat_density(colour="blue", fill=NA) 
  
>  
> # Also works with categorical variables 
> ggplot(movies, aes(x=mpaa)) + stat_bin() 
  
> qplot(mpaa, data=movies, stat="bin") 
  

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© Hadley Wickham 2010