merge_append: Append columns from B to A by keyed join (fast,...

In trtswitch: Treatment Switching

Append columns from B to A by keyed join (fast, data.table-based)

Description

A and B may be data.frame or data.table.

• If A is a data.table it will be modified by reference.

• If A is a data.frame a modified data.frame is returned.

Usage

merge_append(A, B, by_vars, new_vars, overwrite = TRUE, first_match = TRUE)

Arguments

A	left table (data.frame or data.table) — rows preserved/order preserved
B	right table (data.frame or data.table) — must contain by_vars and new_vars
by_vars	character vector of join columns (e.g. c("id","tstart","tstop"))
new_vars	character vector of column names from B to append to A
overwrite	logical: if TRUE, overwrite any existing columns in A with same avar names (default TRUE)
first_match	logical: if TRUE use first match when B has duplicate keys; if FALSE, error on duplicates

Value

If A was a data.frame, returns modified data.frame; if A was data.table returns invisible(NULL).

trtswitch documentation built on Jan. 10, 2026, 5:08 p.m.