Find possible offset terms in a model
Returns a character vector with the name(s) of offset terms.
find_offset(x)
x |
A fitted model. |
A character vector with the name(s) of offset terms.
# Generate some zero-inflated data set.seed(123) N <- 100 # Samples x <- runif(N, 0, 10) # Predictor off <- rgamma(N, 3, 2) # Offset variable yhat <- -1 + x * 0.5 + log(off) # Prediction on log scale dat <- data.frame(y = NA, x, logOff = log(off)) dat$y <- rpois(N, exp(yhat)) # Poisson process dat$y <- ifelse(rbinom(N, 1, 0.3), 0, dat$y) # Zero-inflation process if (require("pscl")) { m1 <- zeroinfl(y ~ offset(logOff) + x | 1, data = dat, dist = "poisson") find_offset(m1) m2 <- zeroinfl(y ~ x | 1, data = dat, offset = logOff, dist = "poisson") find_offset(m2) }
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