summaryBy {doBy} | R Documentation |
Function to calculate groupwise summary statistics, much like the summary procedure of SAS
summaryBy(formula, data = parent.frame(), id = NULL, FUN = mean, keep.names=FALSE, p2d=FALSE, order=TRUE, full.dimension=FALSE, var.names=NULL, fun.names=NULL, ...)
formula |
A formula object, see examples below |
data |
A data frame |
id |
A formula specifying variables which data are not grouped by but which should appear in the output. See examples below. |
FUN |
A list of functions to be applied, see examples below. |
keep.names |
If TRUE and if there is only ONE function in FUN, then the variables in the output will have the same name as the variables in the input, see 'examples'. |
p2d |
Should parentheses in output variable names be replaced by dots? |
order |
Should the resulting dataframe be ordered according to the variables on the right hand side of the formula? (using orderBy |
full.dimension |
If TRUE then rows of summary statistics are repeated such that the result will have the same number of rows as the input dataset. |
var.names |
Option for user to specify the names of the variables on the left hand side. |
fun.names |
Option for user to specify function names to apply to the variables on the left hand side. |
... |
Additional arguments to FUN. This could for example be NA actions. |
Extra arguments ('...') are passed onto the functions in FUN. Hence care must be taken that all functions in FUN accept these arguments - OR one can explicitly write a functions which get around this. This can particularly be an issue in connection with handling NAs. See examples below.
Some code for this function has been suggested by Jim Robison-Cox.
A data frame
Søren Højsgaard, sorenh@math.aau.dk
ave
,
descStat
,
lapplyBy
,
orderBy
,
scaleBy
,
splitBy
,
transformBy
,
data(dietox) dietox12 <- subset(dietox,Time==12) summaryBy(Weight+Feed~Evit+Cu, data=dietox12, FUN=c(mean,var,length)) summaryBy(list(c("Weight","Feed"), c("Evit","Cu")), data=dietox12, FUN=c(mean,var,length)) summaryBy(Weight+Feed~Evit+Cu+Time, data=subset(dietox,Time>1), FUN=c(mean,var,length)) ## Calculations on transformed data: summaryBy(log(Weight)+Feed~Evit+Cu, data=dietox12) ## Calculations on all numerical variables (not mentioned elsewhere): summaryBy(.~Evit+Cu, data=dietox12, id=~Litter, FUN=mean) ## There are missing values in the 'airquality' data, so we remove these ## before calculating mean and variance with 'na.rm=TRUE'. However the ## length function does not accept any such argument. Hence we get ## around this by defining our own summary function in which length is ## not supplied with this argument while mean and var are: sumfun <- function(x, ...){ c(m=mean(x, ...), v=var(x, ...), l=length(x)) } summaryBy(Ozone+Solar.R~Month, data=airquality, FUN=sumfun, na.rm=TRUE) ## Using '.' on the right hand side of a formula means to stratify by ## all variables not used elsewhere: data(warpbreaks) summaryBy(breaks ~ wool+tension, warpbreaks) summaryBy(breaks ~., warpbreaks) summaryBy(.~ wool+tension, warpbreaks) ## Keep the names of the variables (works only if FUN only returns one ## value): summaryBy(Ozone+Wind~Month, data=airquality,FUN=c(mean),na.rm=TRUE, keep.names=TRUE) ## Using full.dimension=TRUE ## Consider: summaryBy(breaks~wool, data=warpbreaks) ## Rows of result are replicated below summaryBy(breaks~wool, data=warpbreaks, full.dimension=TRUE) ## Notice: Previous result is effectively the same as with(warpbreaks, ave(breaks, wool)) ## A possible application of full.dimension=TRUE is if we want to ## standardize (center and scale) data within groups: ss <- summaryBy(breaks~wool, data=warpbreaks, full.dimension=TRUE, FUN=c(mean,sd)) (warpbreaks$breaks-ss$breaks.mean)/ss$breaks.sd