psych (version 1.0-42)

describe.by: Basic summary statistics by group

Description

Report basic summary statistics by a grouping variable. Useful if the grouping variable is some experimental variable and data are to be aggregated for plotting. Just a wrapper for by and describe.

Usage

describe.by(x, group,mat=FALSE,...)

Arguments

x

a data.frame or matrix

group

a grouping variable

mat

provide a matrix output rather than a list

...

parameters to be passed to describe

Value

• A data.frame of the relevant statistics broken down by group: item name item number number of valid cases mean standard deviation median mad: median absolute deviation (from the median) minimum maximum skew standard error

See Also

describe

Examples

set.seed(42)  #to get the same values each time
 x.df <- data.frame(group=sample(2,20,replace=TRUE), matrix(rnorm(100),ncol=5))
 x <- describe.by(x.df,x.df$group)
 x  #shows all the results
 x[1]  #shows just the first group
 x <- matrix(sample(4,200,replace=TRUE),ncol=5)
 y <- describe.by(x,x[,1])
y