mosaic (version 0.14)

compareMean: Compare means between 2 groups

Description

A function to calculate the difference between the means of a continuous variable for two groups.

Usage

compareMean(formula, data = parent.frame(), ...)

Arguments

formula

a formula

data

a data frame in which x is evaluated if x is a formula. Note that the default is data=parent.frame(). This makes it convenient to use this function interactively by treating the working envionment as if it were a data frame. But this may not be appropriate for programming uses. When programming, it is best to use an explicit data argument -- ideally supplying a data frame that contains the variables mentioned

...

other arguments

Value

the difference in means between the second and first group

See Also

do, compareProportion and shuffle

Examples

if (require(mosaicData)) {
  data(HELPrct)
  # calculate the observed difference
  mean(age ~ sex, data=HELPrct)
  obs <- diffmean(age ~ sex, data=HELPrct); obs
  # calculate the permutation distribution
  nulldist <- do(100) * diffmean(age ~ shuffle(sex), 
    data=HELPrct) 
  histogram(~ diffmean, groups=(diffmean >= obs), nulldist, 
    xlab="difference in means")
}