defMiss {simstudy}

Definitions for missing data

Description

Add single row to definitions table for missing data

Usage

defMiss(
  dtDefs = NULL,
  varname,
  formula,
  logit.link = FALSE,
  baseline = FALSE,
  monotonic = FALSE
)

Arguments

dtDefs

Definition data.table to be modified

varname

Name of variable with missingness

formula

Formula to describe pattern of missingness

logit.link

Indicator set to TRUE when the probability of missingness is based on a logit model.

baseline

Indicator is set to TRUE if the variable is a baseline measure and should be missing throughout an entire observation period. This is applicable to repeated measures/longitudinal data.

monotonic

Indicator set to TRUE if missingness at time t is followed by missingness at all follow-up times > t.

Value

A data.table named dtName that is an updated data definitions table

See Also

genMiss, genObs

Examples

def1 <- defData(varname = "m", dist = "binary", formula = .5)
def1 <- defData(def1, "u", dist = "binary", formula = .5)
def1 <- defData(def1, "x1", dist = "normal", formula = "20*m + 20*u", variance = 2)
def1 <- defData(def1, "x2", dist = "normal", formula = "20*m + 20*u", variance = 2)
def1 <- defData(def1, "x3", dist = "normal", formula = "20*m + 20*u", variance = 2)

dtAct <- genData(1000, def1)

defM <- defMiss(varname = "x1", formula = .15, logit.link = FALSE)
defM <- defMiss(defM, varname = "x2", formula = ".05 + m * 0.25", logit.link = FALSE)
defM <- defMiss(defM, varname = "x3", formula = ".05 + u * 0.25", logit.link = FALSE)
defM <- defMiss(defM, varname = "u", formula = 1, logit.link = FALSE) # not observed
defM

# Generate missing data matrix

missMat <- genMiss(dtName = dtAct, missDefs = defM, idvars = "id")
missMat

# Generate observed data from actual data and missing data matrix

dtObs <- genObs(dtAct, missMat, idvars = "id")
dtObs