zibreg {lava} | R Documentation

## Regression model for binomial data with unkown group of immortals

### Description

Regression model for binomial data with unkown group of immortals (zero-inflated binomial regression)

### Usage

    zibreg(formula, formula.p = ~1, data, family = stats::binomial(),
      offset = NULL, start, var = "hessian", ...)

### Arguments

`formula` | Formula specifying
`formula.p` | Formula for model of disease prevalence
`data` | data frame
`family` | Distribution family (see the help page `family`)
`offset` | Optional offset
`start` | Optional starting values
`var` | Type of variance (robust, expected, hessian, outer)
`...` | Additional arguments to lower level functions

### Author(s)

Klaus K. Holst

### Examples

    ## Simulation
    n <- 2e3
    x <- runif(n,0,20)
    age <- runif(n,10,30)
    z0 <- rnorm(n,mean=-1+0.05*age)
    z <- cut(z0,breaks=c(-Inf,-1,0,1,Inf))
    p0 <- lava:::expit(model.matrix(~z+age) %*% c(-.4, -.4, 0.2, 2, -0.05))
    y <- (runif(n)<lava:::tigol(-1+0.25*x-0*age))*1
    u <- runif(n)<p0
    y[u==0] <- 0
    d <- data.frame(y=y,x=x,u=u*1,z=z,age=age)
    head(d)

    ## Estimation
    e0 <- zibreg(y~x*z,~1+z+age,data=d)
    e <- zibreg(y~x,~1+z+age,data=d)
    compare(e,e0)
    e
    PD(e0,intercept=c(1,3),slope=c(2,6))

    B <- rbind(c(1,0,0,0,20),
               c(1,1,0,0,20),
               c(1,0,1,0,20),
               c(1,0,0,1,20))
    prev <- summary(e,pr.contrast=B)$prevalence

    x <- seq(0,100,length.out=100)
    newdata <- expand.grid(x=x,age=20,z=levels(d$z))
    fit <- predict(e,newdata=newdata)
    plot(0,0,type="n",xlim=c(0,101),ylim=c(0,1),xlab="x",ylab="Probability(Event)")
    count <- 0
    for (i in levels(newdata$z)) {
      count <- count+1
      lines(x,fit[which(newdata$z==i)],col="darkblue",lty=count)
    }
    abline(h=prev[3:4,1],lty=3:4,col="gray")
    abline(h=prev[3:4,2],lty=3:4,col="lightgray")
    abline(h=prev[3:4,3],lty=3:4,col="lightgray")
    legend("topleft",levels(d$z),col="darkblue",lty=seq_len(length(levels(d$z))))

[Package lava version 1.5.1 Index]