quest (version 0.2.0)

lengths_by: Length of Data Columns by Group

Description

lengths_by computes the the length of multiple columns in a data.frame by group. The argument na.rm can be used to include (FALSE) or exclude (TRUE) missing values. Through the use of na.rm = TRUE, the number of observed values for each variable by each group can be computed.

Usage

lengths_by(data, vrb.nm, grp.nm, na.rm = FALSE, sep = ".")

Value

data.frame with colnames = vrb.nm and rownames =

length(levels(interaction(grp))) providing the number of elements (excluding missing values if na.rm = TRUE) in each column by group.

Arguments

data

data.frame of data.

vrb.nm

character vector of colnames from data specifying the variables.

grp.nm

character vector of colnames from data specifying the groups.

na.rm

logical vector of length 1 specifying whether to include (FALSE) or exclude (TRUE) missing values.

sep

character vector of length 1 specifying what string should separate different group values when naming the return object. This argument is only used if grp is a list of atomic vectors (e.g., data.frame).

See Also

length_by length colNA

Examples

lengths_by(mtcars, vrb.nm = c("mpg","cyl","disp"), grp = "gear")
lengths_by(mtcars, vrb.nm = c("mpg","cyl","disp"),
   grp = c("gear","vs")) # can handle multiple grouping variables
lengths_by(mtcars, vrb.nm = c("mpg","cyl","disp"),
   grp = c("gear","am")) # can handle zero lengths
lengths_by(airquality, c("Ozone","Solar.R","Wind"), grp = "Month",
   na.rm = FALSE) # include missing values
lengths_by(airquality, c("Ozone","Solar.R","Wind"), grp = "Month",
   na.rm = TRUE) # exclude missing values