Applies a function, typically to compute a single statistic, like a mean, median, or standard deviation,
within levels of a factor or within combinations of levels of two or more factors to produce a table of statistics. This function provides
a formula interface to the standard R `tapply`

function.

`Tapply(formula, fun, data, na.action = na.pass, ..., targs = list())`

formula

a two-sided formula of the form `variable ~ factor.1 + factor.2 + ... + factor.n`

or,
equivalently, `variable ~ factor.1*factor.2* ... *factor.n`

.
The variables on the right-hand side
of the formula are normally factors or are otherwise coerced to factors.

fun

a function, like `mean`

, `median`

, or `sd`

, that takes a vector first argument and typically
returns a single number as its value.

data

an optional data frame within which to find the variable and factor(s).

na.action

…

arguments to pass to the function given in the `fun`

argument, such as (commonly)
`na.rm=TRUE`

.

targs

a list of optional arguments to pass to `tapply`

.

The object returned by `tapply`

, typically simply printed.

The function given by `fun`

is applied to the values of the left-hand-side variable in `formula`

within
(combination of) levels of the factor(s) given in the right-hand side of `formula`

, producing a table of statistics.

Fox, J. and Weisberg, S. (2019)
*An R Companion to Applied Regression*, Third Edition. Sage.

# NOT RUN { Tapply(conformity ~ partner.status + fcategory, mean, data=Moore) Tapply(conformity ~ partner.status + fcategory, mean, data=Moore, trim=0.2) Moore[1, 2] <- NA Tapply(conformity ~ partner.status + fcategory, mean, data=Moore) Tapply(conformity ~ partner.status + fcategory, mean, data=Moore, na.rm=TRUE) Tapply(conformity ~ partner.status + fcategory, mean, data=Moore, na.action=na.omit) # equivalent remove("Moore") # }