Quasi-variances Extraction Function
Takes a rcim fit of the appropriate format and
returns either the quasi-variances or quasi-standard errors.
qvar(object, se = FALSE, ...)
This simple function is ad hoc and simply is equivalent to
computing the quasi-variances
by diag(predict(fit1)[, c(TRUE, FALSE)]) / 2.
This function is for convenience only.
Serious users of quasi-variances ought to understand why and how this
function works.
A vector of quasi-variances or quasi-standard errors.
T. W. Yee.
data("ships", package = "MASS")
Shipmodel <- vglm(incidents ~ type + year + period,
poissonff, offset = log(service),
data = ships, subset = (service > 0))
# Easiest form of input
fit1 <- rcim(Qvar(Shipmodel, "type"), uninormal("explink"), maxit = 99)
qvar(fit1) # Quasi-variances
qvar(fit1, se = TRUE) # Quasi-standard errors
# Manually compute them:
(quasiVar <- exp(diag(fitted(fit1))) / 2) # Version 1
(quasiVar <- diag(predict(fit1)[, c(TRUE, FALSE)]) / 2) # Version 2
(quasiSE <- sqrt(quasiVar))
## Not run: qvplot(fit1, col = "green", lwd = 3, scol = "blue", slwd = 2, las = 1)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.