nrow_by {quest}

Number of Rows in Data by Group

Description

nrow_by computes the nrow of a data.frame by group. nrow_by is simply a wrapper for nrow + agg_dfm.

Usage

nrow_by(data, grp.nm, sep = ".")

Arguments

data

data.frame of data.

grp.nm

character vector of colnames from data specifying the grouping variables.

sep

character vector of length 1 specifying what string to use to separate the groups when naming the return object. sep is only used if grp.nm has length > 1 (aka multiple grouping variables)

Value

atomic vector with names = unique(interaction(data[grp.nm], sep = sep)) and length = length(unique(interaction(data[grp.nm], sep = sep))) providing the nrow for each group.

See Also

ncases_by nrow agg_dfm

Examples

# one grouping variables
tmp_nm <- c("outcome","case","session","trt_time")
dat <- as.data.frame(lmeInfo::Bryant2016)[tmp_nm]
stats_by <- psych::statsBy(dat,
   group = "case") # requires you to include "case" column in dat
nrow_by(data = dat, grp.nm = "case")
dat2 <- as.data.frame(ChickWeight)
nrow_by(data = dat2, grp.nm = "Chick")

# two grouping variables
tmp <- reshape(psych::bfi[1:10, ], varying = 1:25, timevar = "item",
   ids = row.names(psych::bfi)[1:10], direction = "long", sep = "")
tmp_nm <- c("id","item","N","E","C","A","O") # Roxygen runs the whole script
dat3 <- str2str::stack2(tmp[tmp_nm], select.nm = c("N","E","C","A","O"),
   keep.nm = c("id","item"))
nrow_by(dat3, grp.nm = c("id","vrb_names"))