ngrp {quest}

Number of Groups in Data

Description

ngrp computes the number of groups in data given one or more grouping variables. This is simply a combination of unique.data.frame + nrow.

Usage

ngrp(data, grp.nm)

Arguments

data

data.frame of data.

grp.nm

character vector of colnames from data specifying the grouping variables.

Value

integer vector of length 1 specifying the number of groups.

See Also

nrow_ml ncases_ml nrow_by ncases_by

Examples

# one grouping variable
Orthodont2 <- as.data.frame(nlme::Orthodont)
ngrp(Orthodont2, grp.nm = "Subject")
length(unique(Orthodont2$"Subject"))

# two grouping variable
co2 <- as.data.frame(CO2)
ngrp(co2, grp.nm = c("Plant"))
grp_nm <- c("Type","Treatment")
ngrp(co2, grp.nm = grp_nm)
unique.data.frame(co2[grp_nm])

#TODO: how does it handle factor levels with no cases?