Skip to contents

Transform a long-format dataset into the start-stop format

long2start_stop.Rd

This function transforms a data.table like object 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, start_name="start",
                stop_name="stop")

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. The supplied data should include full information for all individuals, e.g. no points in time between the first time and last time per individual should be missing.

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.

varying

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

start_name

A single character string, specifying the name that the "start" variable should have in the resulting data. Defaults to "start".

stop_name

Same as start_name but for the "stop" column.

Details

The created start-stop columns are coded as [start, stop), meaning that they will be overlapping. If non-overlapping intervals are desired, users can simply substract 1 from the stop column.

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), start_name (an integer variable encoding the beginning of the intervals), stop (an integer variable encoding the end of the intervals) and all other variables included in the input data in the start-stop format.

Author

Robin Denz

Examples

library(MatchTime)
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"))
#>       .id start  stop      A      B
#>     <int> <int> <int> <lgcl> <lgcl>
#>  1:     1     1     6  FALSE  FALSE
#>  2:     2     1     6  FALSE  FALSE
#>  3:     3     1     6  FALSE  FALSE
#>  4:     4     1     6  FALSE  FALSE
#>  5:     5     1     6  FALSE  FALSE
#>  6:     6     1     6  FALSE  FALSE
#>  7:     7     1     6  FALSE  FALSE
#>  8:     8     1     6  FALSE  FALSE
#>  9:     9     1     4  FALSE  FALSE
#> 10:     9     4     6   TRUE  FALSE
#> 11:    10     1     4  FALSE  FALSE
#> 12:    10     4     6   TRUE  FALSE