bacr-package {bacr}

Bayesian Adjustment for Confounding

Description

This package implements the Bayesian Adjustment for Confounding (BAC) algorithm for estiamting the Average Causal Effect (ACE) in Generalized Linear Models. It accounts for uncertainty in confounder and effect modifier selection and allows estimation of the ACE for the whole population or for a specific subpopulation.

Details

Package:	bacr
Type:	Package
Version:	1.0.1
Depends:	R(>= 2.13.0), graphics, stats, MCMCpack
Date:	2016-10-23
License:	GPL-2

Author(s)

Chi Wang

Maintainer: Chi Wang <[e-mail]>

References

Wang C, Dominici F, Parmigiani G, Zigler CW. Accounting for Uncertainty in Confounder and Effect Modifier Selection When Estimating Average Causal Effects in Generalized Linear Models.
Biometrics, 71(3): 654-665, 2015.

Examples

######## Note that the example below is for illustration purpose only. ####
######## In practice, larger number of iterations will be needed.##########
##### simulate data ############
n = 200; m = 4
V = matrix(rnorm(n*m),ncol=m)
X = rbinom(n, size=1, prob=exp(V[,1])/(1+exp(V[,1])))
beta = c(1,1,1,0.5)
temp0 = cbind(rep(0,n), V[,1:3]) 
temp1 = cbind(rep(1,n), V[,1:3]) 
Y0 = rbinom(n, size=1, prob=exp(temp0)/(1+exp(temp0)))
Y1 = rbinom(n, size=1, prob=exp(temp1)/(1+exp(temp1)))
Y = Y0
Y[X==1] = Y1[X==1]
Z = as.data.frame(cbind(Y, X, V))
names(Z) = c("Y", "X", paste("V", 1:m, sep=""))
##### run BAC  ################# 
result = bac(data=Z, exposure="X", outcome="Y", confounders=paste("V", 1:m, sep=""), 
            interactors=NULL, familyX="binomial", familyY="binomial", omega=Inf, 
            num_its=5, burnM=1, burnB=1, thin=1)
##### summarize results ########
summary(result)
plot(result)

### Adding interaction terms #############
beta = c(1,1,1,1,1)
temp0 = cbind(rep(0,n), V[,1:3], rep(0,n)*V[,3]) 
temp1 = cbind(rep(1,n), V[,1:3], rep(1,n)*V[,3]) 
Y0 = rbinom(n, size=1, prob=exp(temp0)/(1+exp(temp0)))
Y1 = rbinom(n, size=1, prob=exp(temp1)/(1+exp(temp1)))
Y = Y0
Y[X==1] = Y1[X==1]
Z = as.data.frame(cbind(Y, X, V))
names(Z) = c("Y", "X", paste("V", 1:m, sep=""))
result = bac(data=Z, exposure="X", outcome="Y", confounders=paste("V", 1:m, sep=""), 
            interactors=paste("V", 1:m, sep=""), familyX="binomial", familyY="binomial", 
            omega=Inf, num_its=5, burnM=1, burnB=1, thin=1)
summary(result)
plot(result)

##### Estimate the ACE in the exposed subgroup  #################
result = bac(data=Z, exposure="X", outcome="Y", confounders=paste("V", 1:m, sep=""), 
            interactors=paste("V", 1:m, sep=""), familyX="binomial", familyY="binomial", 
            omega=Inf, num_its=5, burnM=1, burnB=1, thin=1, population=(X==1))
summary(result)
plot(result)