NMdata (version 0.2.3)

egdt: Expand grid of data.tables

Description

Expand grid of data.tables

Usage

egdt(dt1, dt2, quiet)

Value

a data.table that expands combinations of rows in dt1 and dt2.

Arguments

dt1

a data.table.

dt2

another data.table.

quiet

The default is to give some information along the way on what data is found. But consider setting this to TRUE for non-interactive use. Default can be configured using NMdataConf.

Details

Merging works mostly similarly for data.table and data.table. However, for data.table the merge must be done by one or more columns. This means that the convenient way to expand all combinations of all rows in two data.frames is not available for data.tables. This functions provides that functionality. It always returns data.tables.

Examples

df1 <- data.frame(a=1:2,b=3:4)
df2 <- data.frame(c=5:6,d=7:8)
merge(df1,df2)
library(data.table)
## This is not possible
if (FALSE) {
merge(as.data.table(df1),as.data.table(df2),allow.cartesian=TRUE)
}
## Use egdt instead
egdt(as.data.table(df1),as.data.table(df2),quiet=TRUE)
## Dimensions are conveniently listed for interactive use
res <- egdt(as.data.table(df1),as.data.table(df2))