Transition (version 1.0.2)

PreviousDate: Find Previous Test Date for Subject

Description

get_prev_date() identifies the previous test date for individual subjects and timepoints in a longitudinal study.

add_prev_date() interpolates these previous test dates into a data frame for further analysis.

Usage

add_prev_date(
  object,
  subject = "subject",
  timepoint = "timepoint",
  result = "result",
  prev_date = "prev_date"
)
get_prev_date(
  object,
  subject = "subject",
  timepoint = "timepoint",
  result = "result"
)

Value

add_prev_date()

A data.frame based on object, with an added column named as specified by argument prev_date of class Date containing the values of the previous test dates.

get_prev_date()

A vector of class Date, length nrow(object), containing the values of the previous test dates ordered in the exact sequence of the subject and timepoint in object.

Arguments

object

a data.frame (or object coercible by as.data.frame() to a data frame) containing the data to be analysed.

subject

character, name of the column (of type integer or factor) identifying individual study subjects; default "subject".

timepoint

character, name of the column recording time points (as Dates) of testing of subjects; default "timepoint".

result

character, name of the column (of type ordered factor, or binary, see Details) recording test results; default "result".

prev_date

character, name to be used for a new column to record previous test dates; default "prev_date".

Details

See Transitions details.

See Also

data.frame, Dates, ordered factor.

Other transitions: PreviousResult, Transitions, uniques()

Examples

# \dontshow{
Blackmore <- transform(Blackmore, timepoint = as.Date("2000-01-01") + round(age * 365.25),
    result = cut(exercise, breaks = seq(0, 30, 2), labels = paste0("<=", seq(0, 30, 2)[-1]),
        include.lowest = TRUE, ordered_result = TRUE))
# }

 ## Continuing example from `add_transitions()`
  # subject, timepoint and result arguments all defaults and required types
Blackmore |> str()

  # Integer vector of the previous test dates
get_prev_date(Blackmore)

  # Add column of  previous test dates to data frame
add_prev_date(Blackmore) |> head(32)

rm(Blackmore)