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AIPW_base.R
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AIPW_base.R
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#' @title Augmented Inverse Probability Weighting Base Class (AIPW_base)
#'
#' @description A base class for AIPW that implements the common methods, such as \code{summary()} and \code{plot.p_score()}, inheritted by [AIPW] and [AIPW_tmle] class
#'
#' @docType class
#'
#' @importFrom R6 R6Class
#'
#' @return \code{AIPW} base object
#' @seealso [AIPW] and [AIPW_tmle]
#' @format \code{\link{R6Class}} object.
#' @export
AIPW_base <- R6::R6Class(
"AIPW_base",
portable = TRUE,
class = TRUE,
public = list(
#-------------------------public fields-----------------------------#
#Number of observations
n = NULL,
#Number of exposed
n_A1 = NULL,
#Number of unexposed
n_A0 = NULL,
#Fit the outcome model stratified by exposure status (only applicable to AIPW class or manual setup)
stratified_fitted = FALSE,
#Components for estimating the influence functions of all observations to calculate average causal effects
obs_est = list(mu0 = NULL,
mu1 = NULL,
mu = NULL,
raw_p_score = NULL,
p_score = NULL,
ip_weights = NULL,
aipw_eif1 = NULL,
aipw_eif0 = NULL),
#ATE: Risk difference, risk ratio, odds ratio and variance-covariance matrix for SE calculation
estimates = list(risk_A1 = NULL,
risk_A0 = NULL,
RD = NULL,
RR = NULL,
OR = NULL,
sigma_covar = NULL),
#ATT: Risk difference
ATT_estimates = list(RD = NULL),
#ATC: Risk difference
ATC_estimates = list(RD = NULL),
#A matrix contains RD, RR and OR with their SE and 95%CI
result = NULL,
#A density plot of propensity scores by exposure status (`ggplot2::geom_density`)
g.plot = NULL,
#A box plot of inverse probability weights using truncated propensity scores by exposure status (`ggplot2::geom_boxplot`)
ip_weights.plot = NULL,
#-------------------------constructor-----------------------------#
initialize = function(Y=NULL, A=NULL,verbose=TRUE){
#save input into private fields
private$Y=as.numeric(Y)
private$A=as.numeric(A)
private$observed = as.numeric(!is.na(private$Y))
private$verbose=verbose
#check data length
if (length(private$Y)!=length(private$A)){
stop("Please check the dimension of the data")
}
#detect outcome is binary or continuous
if (length(unique(private$Y[!is.na(private$Y)]))==2) {
private$Y.type = 'binomial'
} else {
private$Y.type = 'gaussian'
}
#check missing exposure
if (any(is.na(private$A))){
stop("Missing exposure is not allowed.")
}
#check missing outcome
if (any(private$observed == 0)){
warning("Missing outcome is detected. Analysis assumes missing at random (MAR).")
private$Y.missing = TRUE
}
#setup
private$AxObserved = private$A * private$observed #I(A=a, observed==1)
self$n <- length(private$A)
self$n_A1 <- sum(private$A==1)
self$n_A0 <- sum(private$A==0)
self$obs_est$mu0 <- rep(NA,self$n)
self$obs_est$mu1 <- rep(NA,self$n)
self$obs_est$mu <- rep(NA,self$n)
self$obs_est$raw_p_score <- rep(NA,self$n)
},
#-------------------------summary method-----------------------------#
summary = function(g.bound=0.025){
#p_score truncation
if (length(g.bound) > 2){
warning('More than two `g.bound` are provided. Only the first two will be used.')
g.bound = g.bound[1:2]
} else if (length(g.bound) ==1 & g.bound[1] >= 0.5){
stop("`g.bound` >= 0.5 is not allowed when only one `g.bound` value is provided")
}
private$g.bound=g.bound
#check g.bound value
if (!is.numeric(private$g.bound)){
stop("`g.bound` must be numeric")
} else if (max(private$g.bound) > 1 | min(private$g.bound) < 0){
stop("`g.bound` must between 0 and 1")
}
self$obs_est$p_score <- private$.bound(self$obs_est$raw_p_score)
#inverse probability weights
self$obs_est$ip_weights <- (as.numeric(private$A==1)/self$obs_est$p_score) + (as.numeric(private$A==0)/(1-self$obs_est$p_score))
##------AIPW est------##
#### ATE EIF
self$obs_est$aipw_eif1 <- ifelse(private$observed == 1,
(as.numeric(private$A[private$observed==1]==1)/self$obs_est$p_score[private$observed==1])*
(private$Y[private$observed==1] - self$obs_est$mu[private$observed==1]) +
self$obs_est$mu1[private$observed==1],
0)
self$obs_est$aipw_eif0 <- ifelse(private$observed == 1,
(as.numeric(private$A[private$observed==1]==0)/(1-self$obs_est$p_score[private$observed==1]))*
(private$Y[private$observed==1] - self$obs_est$mu[private$observed==1]) +
self$obs_est$mu0[private$observed==1],
0)
root_n <- sqrt(self$n)
## risk for the treated and controls
self$estimates$risk_A1 <- private$get_RD(self$obs_est$aipw_eif1, 0, root_n)
self$estimates$risk_A0 <- private$get_RD(self$obs_est$aipw_eif0, 0, root_n)
## risk difference
self$estimates$RD <- private$get_RD(self$obs_est$aipw_eif1, self$obs_est$aipw_eif0, root_n)
#results on additive scales
self$result <- cbind(matrix(c(self$estimates$risk_A1, self$estimates$risk_A0,
self$estimates$RD), nrow=3, byrow=T),
c( self$n_A1, self$n_A0,rep(self$n,1)))
row.names(self$result) <- c("Risk of Exposure", "Risk of Control","Risk Difference")
colnames(self$result) <- c("Estimate","SE","95% LCL","95% UCL","N")
if (private$Y.type == 'binomial'){
## var-cov mat for rr and or calculation
self$estimates$sigma_covar <- private$get_sigma_covar(self$obs_est$aipw_eif0,self$obs_est$aipw_eif1)
## risk ratio
self$estimates$RR <- private$get_RR(self$obs_est$aipw_eif1,self$obs_est$aipw_eif0, self$estimates$sigma_covar, root_n)
## odds ratio
self$estimates$OR <- private$get_OR(self$obs_est$aipw_eif1,self$obs_est$aipw_eif0, self$estimates$sigma_covar, root_n)
#w/ results on the multiplicative scale
mult_result <- cbind(matrix(c(self$estimates$RR, self$estimates$OR),nrow=2,byrow=T),self$n)
row.names(mult_result) <- c("Risk Ratio", "Odds Ratio")
self$result <- rbind(self$result, mult_result)
}
#### ATT/ATC
if (self$stratified_fitted) {
#ATT
self$ATT_estimates$RD <- private$get_ATT_RD(mu0 = self$obs_est$mu0[private$observed==1],
p_score = self$obs_est$p_score[private$observed==1],
A_level = 1, root_n=root_n, ATC = F)
self$ATC_estimates$RD <- private$get_ATT_RD(mu0 = self$obs_est$mu1[private$observed==1],
p_score = 1-self$obs_est$p_score[private$observed==1],
A_level = 0, root_n=root_n, ATC = T)
ATT_ATC_result <- matrix(c(self$ATT_estimates$RD, self$n,
self$ATC_estimates$RD, self$n), nrow = 2,byrow = T)
row.names(ATT_ATC_result) <- c("ATT Risk Difference","ATC Risk Difference")
self$result <- rbind(self$result, ATT_ATC_result)
}
#### Change row names for continuous outcome
if (private$Y.type == 'gaussian'){
row.names(self$result) = gsub("Risk", "Mean", row.names(self$result))
}
if (private$verbose){
print(self$result,digit=3)
}
invisible(self)
},
#-------------------------plot.p_score method-----------------------------#
plot.p_score = function(print.ip_weights = F){
#check if ggplot2 library is loaded
if (!any(names(sessionInfo()$otherPkgs) %in% c("ggplot2"))){
stop("`ggplot2` package is not loaded.")
}
plot_data_A = factor(private$A, levels = 0:1)
#input check
if (any(is.na(self$obs_est$raw_p_score))){
stop("Propensity scores are not estimated.")
} else if (is.null(self$obs_est$p_score)) {
#p_score before truncation (estimated ps)
plot_data = data.frame(A = plot_data_A,
p_score= self$obs_est$raw_p_score,
trunc = "Not truncated")
message("ATE has not been calculated.")
} else {
plot_data = rbind(data.frame(A = plot_data_A,
p_score= self$obs_est$raw_p_score,
trunc = "Not truncated"),
data.frame(A = plot_data_A,
p_score= self$obs_est$p_score,
trunc = "Truncated"))
}
self$g.plot = ggplot2::ggplot(data = plot_data,ggplot2::aes(x = p_score, group = A, color = A, fill=A)) +
ggplot2::geom_density(alpha=0.5) +
ggplot2::scale_x_continuous(limits = c(0,1)) +
ggplot2::facet_wrap(~trunc) +
ggtitle("Propensity scores by exposure status") +
theme_bw() +
theme(legend.position = 'bottom')
xlab('Propensity Scores')
print(self$g.plot)
invisible(self)
}
,
#-------------------------plot.ip_weights method-----------------------------#
plot.ip_weights = function(){
#check if ggplot2 library is loaded
if (!any(names(sessionInfo()$otherPkgs) %in% c("ggplot2"))){
stop("`ggplot2` package is not loaded.")
}
plot_data_A = factor(private$A, levels = 0:1)
#input check
if (any(is.na(self$obs_est$raw_p_score))){
stop("Propensity scores are not estimated.")
} else if (is.null(self$obs_est$p_score)) {
stop("ATE has not been calculated.")
} else {
ipw_plot_data = data.frame(A = plot_data_A, ip_weights= self$obs_est$ip_weights)
self$ip_weights.plot = ggplot2::ggplot(data = ipw_plot_data, ggplot2::aes(y = ip_weights, x = A, fill = A)) +
ggplot2::geom_boxplot(alpha=0.5) +
ggtitle("IP-weights using truncated propensity scores by exposure status") +
theme_bw() +
ylab('Inverse Probablity Weights') +
coord_flip() +
theme(legend.position = 'bottom')
print(self$ip_weights.plot)
}
invisible(self)
}
),
#-------------------------private fields and methods----------------------------#
private = list(
#input
Y=NULL,
A=NULL,
observed=NULL,
AxObserved = NULL,
verbose=NULL,
g.bound=NULL,
#outcome type
Y.type = NULL,
Y.missing = FALSE,
#private methods
#Use individual estimates of efficient influence functions (obs_est$aipw_eif0 & obs_est$aipw_eif0) to calculate RD, RR and OR with SE and 95CI%
get_RD = function(aipw_eif1,aipw_eif0,root_n){
est <- mean(aipw_eif1 - aipw_eif0)
se <- stats::sd(aipw_eif1 - aipw_eif0)/root_n
ci <- get_ci(est,se,ratio=F)
output = c(est, se, ci)
names(output) = c("Estimate","SE","95% LCL","95% UCL")
return(output)
},
get_RR = function(aipw_eif1,aipw_eif0,sigma_covar,root_n){
est <- mean(aipw_eif1)/mean(aipw_eif0)
se <- sqrt((sigma_covar[1,1]/(mean(aipw_eif0)^2)) -
(2*sigma_covar[1,2]/(mean(aipw_eif1)*mean(aipw_eif0))) +
(sigma_covar[2,2]/mean(aipw_eif1)^2) -
(2*sigma_covar[1,2]/(mean(aipw_eif1)*mean(aipw_eif0))))/root_n
ci <- get_ci(est,se,ratio=T)
output = c(est, se, ci)
names(output) = c("Estimate","SE","95% LCL","95% UCL")
return(output)
},
get_OR = function(aipw_eif1,aipw_eif0,sigma_covar,root_n){
est <- (mean(aipw_eif1)/(1-mean(aipw_eif1))) / (mean(aipw_eif0)/(1-mean(aipw_eif0)))
se <- sqrt((sigma_covar[1,1]/((mean(aipw_eif0)^2)*(mean(1-aipw_eif0)^2))) -
(2*sigma_covar[1,2]/(mean(aipw_eif1)*mean(aipw_eif0)*mean(1-aipw_eif1)*mean(1-aipw_eif0))) +
(sigma_covar[2,2]/((mean(aipw_eif1)^2)*(mean(1-aipw_eif1)^2))) -
(2*sigma_covar[1,2]/(mean(aipw_eif1)*mean(aipw_eif0)
*mean(1-aipw_eif1)*mean(1-aipw_eif0))))/root_n
ci <- get_ci(est,se,ratio=T)
output = c(est, se, ci)
names(output) = c("Estimate","SE","95% LCL","95% UCL")
return(output)
},
get_sigma_covar = function(aipw_eif0,aipw_eif1){
mat <- matrix(c(stats::var(aipw_eif0),
stats::cov(aipw_eif0,aipw_eif1),
stats::cov(aipw_eif1,aipw_eif0),
stats::var(aipw_eif1)),nrow=2)
return(mat)
},
#ATT/ATC calculation
get_ATT_RD = function(A =private$A[private$observed==1], Y = private$Y[private$observed==1],
mu0, p_score, A_level, root_n, ATC = F){
I_A = (A==A_level) / mean(A==A_level)
I_A_com = (1-A==A_level) / mean(1-(A==A_level))
eif <- I_A*Y - (I_A*(mu0) + I_A_com*(Y-mu0)*p_score/(1-p_score))
est <- mean(eif)
if (ATC){
est <- -1 * est
}
se <- stats::sd(eif - I_A*est)/root_n
ci <- get_ci(est,se,ratio=F)
output = c(est, se, ci)
names(output) = c("Estimate","SE","95% LCL","95% UCL")
return(output)
},
#setup the bounds for the propensity score to ensure the balance
.bound = function(p_score,bound = private$g.bound){
if (length(bound) == 1){
res <- base::ifelse(p_score<bound, bound,
base::ifelse(p_score > (1-bound), (1-bound) ,p_score))
} else {
res <- base::ifelse(p_score< min(bound), min(bound),
base::ifelse(p_score > max(bound), max(bound), p_score))
}
return(res)
}
)
)
#' @name summary
#' @aliases summary.AIPW_base
#' @title Summary of the average treatment effects from AIPW
#'
#' @description
#' Calculate average causal effects in RD, RR and OR in the fitted [AIPW] or [AIPW_tmle] object using the estimated efficient influence functions
#'
#' @section R6 Usage:
#' \code{$summary(g.bound = 0.025)} \cr
#' \code{$summary(g.bound = c(0.025,0.975))}
#'
#' @param g.bound Value between \[0,1\] at which the propensity score should be truncated.
#' Propensity score will be truncated to \eqn{[g.bound, 1-g.bound]} when one g.bound value is provided, or to \eqn{[min(g.bound), max(g.bound)]} when two values are provided.
#' \strong{Defaults to 0.025}.
#'
#' @seealso [AIPW] and [AIPW_tmle]
#'
#' @return `estimates` and `result` (public variables): Risks, Average treatment effect in RD, RR and OR.
NULL
#' @name plot.p_score
#' @title Plot the propensity scores by exposure status
#'
#' @description
#' Plot and check the balance of propensity scores by exposure status
#'
#' @section R6 Usage:
#' \code{$plot.p_plot()}
#'
#' @seealso [AIPW] and [AIPW_tmle]
#'
#' @return `g.plot` (public variable): A density plot of propensity scores by exposure status (`ggplot2::geom_density`)
NULL
#' @name plot.ip_weights
#' @title Plot the inverse probability weights using truncated propensity scores by exposure status
#'
#' @description
#' Plot and check the balance of propensity scores by exposure status
#'
#' @section R6 Usage:
#' \code{$plot.ip_weights()}
#'
#' @seealso [AIPW] and [AIPW_tmle]
#'
#' @return `ip_weights.plot` (public variable): A box plot of inverse probability weights using truncated propensity scores by exposure status (`ggplot2::geom_boxplot`)
NULL