inst/doc/smcfcs-vignette.R

In smcfcs: Multiple Imputation of Covariates by Substantive Model Compatible Fully Conditional Specification

## -----------------------------------------------------------------------------
library(smcfcs)
ex_linquad[1:10,]

## -----------------------------------------------------------------------------
set.seed(123)
#impute missing values in x, compatibly with quadratic substantive model
imps <- smcfcs(ex_linquad, smtype="lm", smformula="y~z+x+xsq",method=c("","","norm","x^2",""))

## -----------------------------------------------------------------------------
# fit substantive model
library(mitools)
impobj <- imputationList(imps$impDatasets)
models <- with(impobj, lm(y~z+x+xsq))
summary(MIcombine(models))

## -----------------------------------------------------------------------------
#impute missing values in x, compatibly with model for y which omits the quadratic effect
imps <- smcfcs(ex_linquad, smtype="lm", smformula="y~z+x",method=c("","","norm","x^2",""))

## -----------------------------------------------------------------------------
# fit substantive model
impobj <- imputationList(imps$impDatasets)
models <- with(impobj, lm(y~z+x+xsq))
summary(MIcombine(models))

## -----------------------------------------------------------------------------
#impute, including v as a covariate in the substantive/outcome model
imps <- smcfcs(ex_linquad, smtype="lm", smformula="y~z+x+xsq+v",method=c("","","norm","x^2",""))
# fit substantive model, which omits v
impobj <- imputationList(imps$impDatasets)
models <- with(impobj, lm(y~z+x+xsq))
summary(MIcombine(models))

## -----------------------------------------------------------------------------
predMatrix <- array(0, dim=c(ncol(ex_linquad),ncol(ex_linquad)))
predMatrix[3,] <- c(0,1,0,0,1)
imps <- smcfcs(ex_linquad, smtype="lm", smformula="y~z+x+xsq",method=c("","","norm","x^2",""),predictorMatrix=predMatrix)
impobj <- imputationList(imps$impDatasets)
models <- with(impobj, lm(y~z+x+xsq))
summary(MIcombine(models))

## ---- fig.width = 6, fig.height = 4-------------------------------------------
# impute once with a larger number of iterations than the default 10
imps <- smcfcs(ex_linquad, smtype="lm", smformula="y~z+x+xsq",method=c("","","norm","x^2",""),predictorMatrix=predMatrix,m=1,numit=100)
# plot estimates of the fourth parameter of the substantive model against iteration number
plot(imps$smCoefIter[1,4,])