```
# NOT RUN {
quasibinomialff()
quasibinomialff(link = "probit")
# Nonparametric logistic regression
hunua <- transform(hunua, a.5 = sqrt(altitude)) # Transformation of altitude
fit1 <- vglm(agaaus ~ poly(a.5, 2), quasibinomialff, hunua)
fit2 <- vgam(agaaus ~ s(a.5, df = 2), quasibinomialff, hunua)
# }
# NOT RUN {
plot(fit2, se = TRUE, llwd = 2, lcol = "orange", scol = "orange",
xlab = "sqrt(altitude)", ylim = c(-3, 1),
main = "GAM and quadratic GLM fitted to species data")
plotvgam(fit1, se = TRUE, lcol = "blue", scol = "blue", add = TRUE, llwd = 2)
# }
# NOT RUN {
fit1@misc$dispersion # dispersion parameter
logLik(fit1)
# Here, the dispersion parameter defaults to 1
fit0 <- vglm(agaaus ~ poly(a.5, 2), binomialff, hunua)
fit0@misc$dispersion # dispersion parameter
# }
```

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