long2start_stop {simDAG}

Transform a data.table in the long-format to a data.table in the start-stop format

Description

This function transforms a data.table in the long-format (one row per person per time point) to a data.table in the start-stop format (one row per person-specific period in which no variables changed).

Usage

long2start_stop(data, id, time, varying, overlap=FALSE,
                check_inputs=TRUE)

Arguments

data

A data.table or an object that can be coerced to a data.table (such as a data.frame) including data in the long-format.

id

A single character string specifying a unique person identifier included in in data.

time

A single character string specifying a time variable included in in data coded as integers starting from 1.

varying

A character vector specifying names of variables included in in data that may change over time.

overlap

Specifies whether the intervals should overlap or not. If TRUE, the "stop" column is simply increased by one, as compared to the output when overlap=FALSE. This means that changes for a given t are recorded at the start of the next interval, but the previous interval ends on that same day.

check_inputs

Whether to check if the user input is correct or not. Can be turned off by setting it to FALSE to save computation time.

Details

This function relies on data.table syntax to make the data transformation as RAM efficient and fast as possible.

Value

Returns a data.table containing the columns .id (the unique person identifier), .time (an integer variable encoding the time) and all other variables included in the input data in the long format.

Author(s)

Robin Denz

Examples

library(simDAG)
library(data.table)

# generate example data in long format
long <- data.table(.id=rep(seq_len(10), each=5),
                   .time=rep(seq_len(5), 10),
                   A=c(rep(FALSE, 43), TRUE, TRUE, rep(FALSE, 3), TRUE,
                           TRUE),
                   B=FALSE)
setkey(long, .id, .time)

# transform to start-stop format
long2start_stop(data=long, id=".id", time=".time", varying=c("A", "B"))