deterministic.g.function_template: Deterministic g/Q functions - examples and templates

In ltmle: Longitudinal Targeted Maximum Likelihood Estimation

Deterministic g/Q functions - examples and templates

Description

Template for the deterministic.g.function argument to ltmle or ltmleMSM.

Usage

deterministic.g.function_template(data, current.node, nodes)

deterministic.Q.function_template(
  data,
  current.node,
  nodes,
  called.from.estimate.g
)

Arguments

data	the 'data' data.frame passed to ltmle or ltmleMSM
current.node	the column index of data corresponding to the A or C node (for g) or L or Y node (for Q)
nodes	list of column indicies, components: A Anodes (treatment) C Cnodes (censoring) L Lnodes (time-varying covariates) Y Ynodes (events) AC Anodes and Cnodes combined and sorted LY Lnodes and Ynodes combined, sorted, "blocks" removed - see ltmle
called.from.estimate.g	TRUE or FALSE - your function will be called with called.from.estimate.g=TRUE during estimation of g and called.from.estimate.g=FALSE during estimation of Q.

Details

MaintainTreatment and MaintainControl are two commonly used deterministic.g.functions.

The intended use of the templates is for the user to copy and paste the function arguments and body and then fill in the required sections. They will not run as-is. Note that there are no comments in the functions as saved. Versions with comments may be found in Examples section below.

MaintainTreatment and MaintainControl may be passed as-is for the deterministic.g.function argument to ltmle or ltmleMSM

Note that censoring nodes in data may be passed as binaries but they are converted to the preferred format of factors with levels "censored" and "uncensored" before deterministic functions are called. Also note that nodes may be passed to ltmle as either the names of nodes or numerical column indicies, but they are all converted to numerical indicies before deterministic functions are called. If the survivalFunction argument to ltmle or ltmleMSM is TRUE, the package automatically assumes that once Y jumps to 1, all future Y nodes stay 1 and treatment does not change. It is not necessary to specify this in deterministic functions.

Value

A deterministic.g.function should return a list with components:

is.deterministic	vector of logicals, length=nrow(data)
prob1	the probability that data[is.deterministic, current.node] == 1, vector of length 1 or length(which(is.deterministic))

A deterministic.Q.function should return a list with components:

is.deterministic	vector of logicals, length=nrow(data)
Q.value	the iterated expectation of the final Y, vector of length 1 or length(which(is.deterministic))

NOTE: The Q.value component is not used or required when called.from.estimate.g is TRUE

Functions

• deterministic.Q.function_template(): Template for the deterministic.Q.function argument to ltmle or ltmleMSM.

Author(s)

Joshua Schwab [e-mail]

See Also

ltmle, ltmleMSM

Examples

# Show template for a deterministic.g.function (comments will not be
# shown, see below for comments)
deterministic.g.function_template

# Show template for a deterministic.Q.function (comments will not be
# shown, see below for comments)
deterministic.Q.function_template

# Use MaintainTreatment
set.seed(1)
rexpit <- function(x) rbinom(n = length(x), size = 1, prob = plogis(x))
n <- 100
W <- rnorm(n)
A1 <- rexpit(W)
A2 <- as.numeric(rexpit(W) | A1)  #treatment at time 1 implies treatment at time 2
Y <- rexpit(W + A1 + A2 + rnorm(n))
data <- data.frame(W, A1, A2, Y)

result <- ltmle(data, Anodes = c("A1", "A2"), Ynodes = "Y", abar = c(1, 1), 
    deterministic.g.function = MaintainTreatment)

# deterministic.g.function_template with comments:

deterministic.g.function_template <- function(data, current.node, nodes) {
    # data: the 'data' data.frame passed to ltmle/ltmleMSM current.node: the
    # column index of data corresponding to the A or C node (see
    # is.deterministic below) nodes: list of column indicies, components: A,
    # C, L, Y, AC (Anodes and Cnodes combined and sorted), LY (Lnodes and
    # Ynodes combined, sorted, 'blocks' removed - see ?ltmle) Note that nodes
    # may be passed to ltmle as either the names of nodes or numerical column
    # indicies, but they are all converted to numerical indicies before
    # deterministic.g.function is called
    
    # deterministic.g.function will be called at all Anodes and Cnodes
    # return(NULL) is equivalent to return(list(is.deterministic=rep(FALSE,
    # nrow(data)), prob1=numeric(0)))
    
    # define is.deterministic here: vector of logicals, length=nrow(data)
    # define prob1 here: the probability that data[is.deterministic,
    # current.node] == 1, vector of length 1 or
    # length(which(is.deterministic))
    is.deterministic <- stop("replace me!")
    prob1 <- stop("replace me!")
    return(list(is.deterministic = is.deterministic, prob1 = prob1))
}

# deterministic.Q.function_template with comments:

deterministic.Q.function_template <- function(data, current.node, nodes, 
    called.from.estimate.g) {
    # data: the 'data' data.frame passed to ltmle/ltmleMSM current.node: the
    # column index of data corresponding to the A or C node (see
    # is.deterministic below) nodes: list of column indicies, components: A,
    # C, L, Y, AC (Anodes and Cnodes combined and sorted), LY (Lnodes and
    # Ynodes combined, sorted, 'blocks' removed - see ?ltmle)
    # called.from.estimate.g: TRUE or FALSE - your function will be called
    # with called.from.estimate.g=TRUE during estimation of g and
    # called.from.estimate.g=FALSE during estimation of Q. During estimation
    # of g, only the is.deterministic element of the return list will be
    # used.  Note that nodes may be passed to ltmle as either the names of
    # nodes or numerical column indicies, but they are all converted to
    # numerical indicies before deterministic.Q.function is called
    
    # It is not necessary to specify that deterministic Y events (Y==1)
    # indicate a deterministic Q value of 1; this is automatic 
    # if the survivalFunction input to ltmle/ltmleMSM is TRUE.
    # deterministic.Q.function will be called at all Lnodes and Ynodes (after
    # removing 'blocks') and Anodes and Cnodes (see called.from.estimate.g
    # above) return(NULL) is equivalent to
    # return(list(is.deterministic=rep(FALSE, nrow(data)),
    # Q.value=numeric(0)))
    
    # define is.deterministic here: vector of logicals, length=nrow(data)
    # define Q.value here: the iterated expectation of the final Y, vector of
    # length 1 or length(which(is.deterministic))
    is.deterministic <- stop("replace me!")
    Q.value <- stop("replace me!")
    return(list(is.deterministic = is.deterministic, Q.value = Q.value))
}

ltmle documentation built on April 15, 2023, 5:06 p.m.