Add information from start-stop data to a match_time object

This function may be used to add variables saved in the start-stop format to a match_time object created using the match_time function. For example, there might be a time-varying variable that was not included in the original data used in the match_time call to save memory, that should now be added later. Using this function, the value of these variables at .treat_time will be added to the data in the match_time object.

Usage

add_from_start_stop(x, data, variable, id=x$id,
                    start="start", stop="stop", default=NA)

Arguments

x: A match_time object created using the match_time function.
data: A data.table like object including at least four columns: id (the unique case identifier), start (beginning of interval), stop (end of interval) and one or more columns defined by the variables argument. May also be any object that can be coerced to be a data.table, such as a data.frame or a tibble. The dataset should be in the same start-stop format that would be required for a regular match_time call.
id: A single character string specifying a column in data, specifying the unique case identifier. By default the same name that was used in the original match_time is used here.
variable: A single character string specifying a variable in data which should be added to the $data object inside of x. Note that if x$data already contains columns with the same names as in variables, an error will be produced.
start: A single character string specifying a column in data specifying the beginning of a time-interval. Defaults to "start".
stop: A single character string specifying a column in data specifying the end of a time-interval. Defaults to "stop".
default: A single value that should be used as default if no information can be found in data for the required point in time for some individuals. If the supplied data does not contain information for some id at .treat_time, this default value will be used instead.

Details

Although this function may be useful for very large datasets, if RAM is not an issue we recommend using the merge_start_stop or similar functions to create a single start-stop dataset to use in match_time instead. This way, all information contained in the start-stop dataset is automatically included in the output as well, without the need to use this function.

Value

Returns a modified match_time object. It is essentially the same object as the supplied x, but it also contains a new column: name (the time of occurence of the next event).

Author

Robin Denz

Examples

library(data.table)
library(MatchTime)

# only execute if packages are available
if (requireNamespace("survival") & requireNamespace("MatchIt")) {

library(survival)
library(MatchIt)

# set random seed to make the output replicably
set.seed(1234)

# load "heart" data from survival package
data("heart")
heart <- heart[, c("id", "start", "stop", "transplant", "age", "surgery")]

}