CJ.dt: grid expand an arbitrary number of data.tables

In kaufman-lab/intervalaverage: Time-Weighted Averaging for Interval Data

grid expand an arbitrary number of data.tables

Description

similar to data.table::CJ and base::expand.grid except for rows of data.tables.

Usage

CJ.dt(..., groups = NULL)

Arguments

...	data.tables
groups	a character vector corresponding to column names of grouping vars in all of the data.tables

Details

CJ.dt computes successive cartesian join over rows of each table paying no attention to whatever the tables are keyed on.

Examples

#' CJ.dt(data.table(c(1,2,2),c(1,1,1)),data.table(c("a","b"),c("c","d")))
#If you want to expand x to unique values of a non-unique columns in y
x <- data.table(c(1,2,3),c("a","b","b"))
y <- data.table(id=c(1,2,2,1,3),value=c(2,4,1,7,3))
z <- CJ.dt(x, y[,list(id=unique(id))])
#if you want to merge this back to y
y[z,on="id",allow.cartesian=TRUE] #or z[y,on="id",allow.cartesian=TRUE]

kaufman-lab/intervalaverage documentation built on Feb. 4, 2023, 9:19 a.m.