Make a two-by-two table

Makes a two-by-two contingency table which takes the visual form:

	Outcome	observed
	Yes	No
Treatment	A	B
Comparator	C	D

Where A, B, C, and D are the distinct number of subjects satisfying the criteria of each 2x2 cell.

Only observations that have a Treatment value recorded are returned.

Usage

make_two_by_two_(
  dat,
  event_index,
  cell_index,
  treatment_var,
  treatment_refval,
  subjectid_var
)

Arguments

dat

data.table. The analysis data set.

event_index

vector of integers that index the rows in dat that match the definition of an 'event'. Matching is done via the INDEX_ column in dat.

cell_index

A vector of integers referencing the rows of dat (as specified by the INDEX_ column in dat) that match the population to be analyzed. See the "Endpoint Events" vignette in ramnog for more information.

treatment_var

character. The name of the treatment variable in dat.

treatment_refval

character. The reference value of the treatment variable in dat.

subjectid_var

character. Name of the subject identifier variable in dat (default is "USUBJID").

Value

A matrix

Examples

dat <- data.table::data.table(
  USUBJID = c("S1", "S2", "S3", "S4", "S5", "S6"),
  TRT     = c("Active", "Active", "Active", "Placebo", "Placebo", "Placebo")
)
dat[, INDEX_ := .I]
#>    USUBJID     TRT INDEX_
#>     <char>  <char>  <int>
#> 1:      S1  Active      1
#> 2:      S2  Active      2
#> 3:      S3  Active      3
#> 4:      S4 Placebo      4
#> 5:      S5 Placebo      5
#> 6:      S6 Placebo      6
data.table::setkey(dat, INDEX_)
make_two_by_two_(dat, event_index = c(1L, 2L, 4L),
                 cell_index = dat[["INDEX_"]],
                 treatment_var = "TRT", treatment_refval = "Placebo",
                 subjectid_var = "USUBJID")
#>         outcome_YES outcome_NO
#> Placebo           1          2
#> Active            2          1