- fit <- optim(start, fn = nll, lower=lower, method='L-BFGS-B', hessian=TRUE, control=list(maxit=1e6))
- return(fit)
-}
-
-## Experimental, and not necessary if errors are independent.
-measerr_irr_mle <- function(df, outcome_formula, outcome_family=gaussian(), rater_formula, proxy_formula, proxy_family=binomial(link='logit'), truth_formula, truth_family=binomial(link='logit')){
-
- ### in this scenario, the ground truth also has measurement error, but we have repeated measures for it.
-
- ## probability of y given observed data.
- df.obs <- df[!is.na(x.obs.1)]
- proxy.variable <- all.vars(proxy_formula)[1]
- df.x.obs.1 <- copy(df.obs)[,x:=1]
- df.x.obs.0 <- copy(df.obs)[,x:=0]
- y.obs <- df.obs[,y]
-
- nll <- function(params){
- outcome.model.matrix.x.obs.0 <- model.matrix(outcome_formula, df.x.obs.0)
- outcome.model.matrix.x.obs.1 <- model.matrix(outcome_formula, df.x.obs.1)
-
- param.idx <- 1
- n.outcome.model.covars <- dim(outcome.model.matrix.x.obs.0)[2]
- outcome.params <- params[param.idx:n.outcome.model.covars]
- param.idx <- param.idx + n.outcome.model.covars
-
- sigma.y <- params[param.idx]
- param.idx <- param.idx + 1
-
- ll.y.x.obs.0 <- dnorm(y.obs, outcome.params %*% t(outcome.model.matrix.x.obs.0),sd=sigma.y, log=TRUE)
- ll.y.x.obs.1 <- dnorm(y.obs, outcome.params %*% t(outcome.model.matrix.x.obs.1),sd=sigma.y, log=TRUE)
-
- ## assume that the two coders are statistically independent conditional on x
- ll.x.obs.0.x0 <- vector(mode='numeric', length=nrow(df.obs))
- ll.x.obs.1.x0 <- vector(mode='numeric', length=nrow(df.obs))
- ll.x.obs.0.x1 <- vector(mode='numeric', length=nrow(df.obs))
- ll.x.obs.1.x1 <- vector(mode='numeric', length=nrow(df.obs))
-
- rater.model.matrix.x.obs.0 <- model.matrix(rater_formula, df.x.obs.0)
- rater.model.matrix.x.obs.1 <- model.matrix(rater_formula, df.x.obs.1)
-
- n.rater.model.covars <- dim(rater.model.matrix.x.obs.0)[2]
- rater.0.params <- params[param.idx:(n.rater.model.covars + param.idx - 1)]
- param.idx <- param.idx + n.rater.model.covars
-
- rater.1.params <- params[param.idx:(n.rater.model.covars + param.idx - 1)]
- param.idx <- param.idx + n.rater.model.covars
-
- # probability of rater 0 if x is 0 or 1
- ll.x.obs.0.x0[df.obs$x.obs.0==1] <- plogis(rater.0.params %*% t(rater.model.matrix.x.obs.0[df.obs$x.obs.0==1,]), log=TRUE)
- ll.x.obs.0.x0[df.obs$x.obs.0==0] <- plogis(rater.0.params %*% t(rater.model.matrix.x.obs.0[df.obs$x.obs.0==0,]), log=TRUE, lower.tail=FALSE)
- ll.x.obs.0.x1[df.obs$x.obs.0==1] <- plogis(rater.0.params %*% t(rater.model.matrix.x.obs.1[df.obs$x.obs.0==1,]), log=TRUE)
- ll.x.obs.0.x1[df.obs$x.obs.0==0] <- plogis(rater.0.params %*% t(rater.model.matrix.x.obs.1[df.obs$x.obs.0==0,]), log=TRUE, lower.tail=FALSE)
-
- # probability of rater 1 if x is 0 or 1
- ll.x.obs.1.x0[df.obs$x.obs.1==1] <- plogis(rater.1.params %*% t(rater.model.matrix.x.obs.0[df.obs$x.obs.1==1,]), log=TRUE)
- ll.x.obs.1.x0[df.obs$x.obs.1==0] <- plogis(rater.1.params %*% t(rater.model.matrix.x.obs.0[df.obs$x.obs.1==0,]), log=TRUE, lower.tail=FALSE)
- ll.x.obs.1.x1[df.obs$x.obs.1==1] <- plogis(rater.1.params %*% t(rater.model.matrix.x.obs.1[df.obs$x.obs.1==1,]), log=TRUE)
- ll.x.obs.1.x1[df.obs$x.obs.1==0] <- plogis(rater.1.params %*% t(rater.model.matrix.x.obs.1[df.obs$x.obs.1==0,]), log=TRUE, lower.tail=FALSE)
-
- proxy.model.matrix.x0 <- model.matrix(proxy_formula, df.x.obs.0)
- proxy.model.matrix.x1 <- model.matrix(proxy_formula, df.x.obs.1)
-
- n.proxy.model.covars <- dim(proxy.model.matrix.x0)[2]
- proxy.params <- params[param.idx:(n.proxy.model.covars+param.idx-1)]
- param.idx <- param.idx + n.proxy.model.covars
-
- proxy.obs <- with(df.obs, eval(parse(text=proxy.variable)))
-
- if( (proxy_family$family=="binomial") & (proxy_family$link=='logit')){
- ll.w.obs.x0 <- vector(mode='numeric',length=dim(proxy.model.matrix.x0)[1])
- ll.w.obs.x1 <- vector(mode='numeric',length=dim(proxy.model.matrix.x1)[1])
-
- # proxy_formula likelihood using logistic regression
- ll.w.obs.x0[proxy.obs==1] <- plogis(proxy.params %*% t(proxy.model.matrix.x0[proxy.obs==1,]),log=TRUE)
- ll.w.obs.x0[proxy.obs==0] <- plogis(proxy.params %*% t(proxy.model.matrix.x0[proxy.obs==0,]),log=TRUE, lower.tail=FALSE)
-
- ll.w.obs.x1[proxy.obs==1] <- plogis(proxy.params %*% t(proxy.model.matrix.x1[proxy.obs==1,]),log=TRUE)
- ll.w.obs.x1[proxy.obs==0] <- plogis(proxy.params %*% t(proxy.model.matrix.x1[proxy.obs==0,]),log=TRUE, lower.tail=FALSE)
- }
-
- ## assume that the probability of x is a logistic regression depending on z
- truth.model.matrix.obs <- model.matrix(truth_formula, df.obs)
- n.truth.params <- dim(truth.model.matrix.obs)[2]
- truth.params <- params[param.idx:(n.truth.params + param.idx - 1)]
-
- ll.obs.x0 <- plogis(truth.params %*% t(truth.model.matrix.obs), log=TRUE)
- ll.obs.x1 <- plogis(truth.params %*% t(truth.model.matrix.obs), log=TRUE, lower.tail=FALSE)
-
- ll.obs <- colLogSumExps(rbind(ll.y.x.obs.0 + ll.x.obs.0.x0 + ll.x.obs.1.x0 + ll.obs.x0 + ll.w.obs.x0,
- ll.y.x.obs.1 + ll.x.obs.0.x1 + ll.x.obs.1.x1 + ll.obs.x1 + ll.w.obs.x1))
-
- ### NOW FOR THE FUN PART. Likelihood of the unobserved data.
- ### we have to integrate out x.obs.0, x.obs.1, and x.
-
-
- ## THE OUTCOME
- df.unobs <- df[is.na(x.obs)]
- df.x.unobs.0 <- copy(df.unobs)[,x:=0]
- df.x.unobs.1 <- copy(df.unobs)[,x:=1]
- y.unobs <- df.unobs$y
-
- outcome.model.matrix.x.unobs.0 <- model.matrix(outcome_formula, df.x.unobs.0)
- outcome.model.matrix.x.unobs.1 <- model.matrix(outcome_formula, df.x.unobs.1)
-
- ll.y.unobs.x0 <- dnorm(y.unobs, outcome.params %*% t(outcome.model.matrix.x.unobs.0), sd=sigma.y, log=TRUE)
- ll.y.unobs.x1 <- dnorm(y.unobs, outcome.params %*% t(outcome.model.matrix.x.unobs.1), sd=sigma.y, log=TRUE)
-
-
- ## THE UNLABELED DATA
-
-
- ## assume that the two coders are statistically independent conditional on x
- ll.x.unobs.0.x0 <- vector(mode='numeric', length=nrow(df.unobs))
- ll.x.unobs.1.x0 <- vector(mode='numeric', length=nrow(df.unobs))
- ll.x.unobs.0.x1 <- vector(mode='numeric', length=nrow(df.unobs))
- ll.x.unobs.1.x1 <- vector(mode='numeric', length=nrow(df.unobs))
-
- df.x.unobs.0[,x.obs := 1]
- df.x.unobs.1[,x.obs := 1]
-
- rater.model.matrix.x.unobs.0 <- model.matrix(rater_formula, df.x.unobs.0)
- rater.model.matrix.x.unobs.1 <- model.matrix(rater_formula, df.x.unobs.1)
-
-
- ## # probability of rater 0 if x is 0 or 1
- ## ll.x.unobs.0.x0 <- colLogSumExps(rbind(plogis(rater.0.params %*% t(rater.model.matrix.x.unobs.0), log=TRUE),
- ## plogis(rater.0.params %*% t(rater.model.matrix.x.unobs.0), log=TRUE, lower.tail=TRUE)))
-
- ## ll.x.unobs.0.x1 <- colLogSumExps(rbind(plogis(rater.0.params %*% t(rater.model.matrix.x.unobs.1), log=TRUE),
- ## plogis(rater.0.params %*% t(rater.model.matrix.x.unobs.1), log=TRUE, lower.tail=TRUE)))
-
- ## # probability of rater 1 if x is 0 or 1
- ## ll.x.unobs.1.x0 <- colLogSumExps(rbind(plogis(rater.1.params %*% t(rater.model.matrix.x.unobs.0), log=TRUE),
- ## plogis(rater.1.params %*% t(rater.model.matrix.x.unobs.0), log=TRUE, lower.tail=TRUE)))
-
- ## ll.x.unobs.1.x1 <- colLogSumExps(rbind(plogis(rater.1.params %*% t(rater.model.matrix.x.unobs.1), log=TRUE),
- ## plogis(rater.1.params %*% t(rater.model.matrix.x.unobs.1), log=TRUE, lower.tail=TRUE)))
-
-
- proxy.unobs <- with(df.unobs, eval(parse(text=proxy.variable)))
- proxy.model.matrix.x0.unobs <- model.matrix(proxy_formula, df.x.unobs.0)
- proxy.model.matrix.x1.unobs <- model.matrix(proxy_formula, df.x.unobs.1)
-
- if( (proxy_family$family=="binomial") & (proxy_family$link=='logit')){
- ll.w.unobs.x0 <- vector(mode='numeric',length=dim(proxy.model.matrix.x0)[1])
- ll.w.unobs.x1 <- vector(mode='numeric',length=dim(proxy.model.matrix.x1)[1])
-
-
- # proxy_formula likelihood using logistic regression
- ll.w.unobs.x0[proxy.unobs==1] <- plogis(proxy.params %*% t(proxy.model.matrix.x0.unobs[proxy.unobs==1,]),log=TRUE)
- ll.w.unobs.x0[proxy.unobs==0] <- plogis(proxy.params %*% t(proxy.model.matrix.x0.unobs[proxy.unobs==0,]),log=TRUE, lower.tail=FALSE)
-
- ll.w.unobs.x1[proxy.unobs==1] <- plogis(proxy.params %*% t(proxy.model.matrix.x1.unobs[proxy.unobs==1,]),log=TRUE)
- ll.w.unobs.x1[proxy.unobs==0] <- plogis(proxy.params %*% t(proxy.model.matrix.x1.unobs[proxy.unobs==0,]),log=TRUE, lower.tail=FALSE)
- }
-
- truth.model.matrix.unobs <- model.matrix(truth_formula, df.unobs)
-
- ll.unobs.x0 <- plogis(truth.params %*% t(truth.model.matrix.unobs), log=TRUE)
- ll.unobs.x1 <- plogis(truth.params %*% t(truth.model.matrix.unobs), log=TRUE, lower.tail=FALSE)
-
- ll.unobs <- colLogSumExps(rbind(ll.unobs.x0 + ll.w.unobs.x0 + ll.y.unobs.x0,
- ll.unobs.x1 + ll.w.unobs.x1 + ll.y.unobs.x1))
-
- return(-1 *( sum(ll.obs) + sum(ll.unobs)))
- }
-
- outcome.params <- colnames(model.matrix(outcome_formula,df))
- lower <- rep(-Inf, length(outcome.params))
-
- if(outcome_family$family=='gaussian'){
- params <- c(outcome.params, 'sigma_y')
- lower <- c(lower, 0.00001)