# NOT RUN { logitlink("a") logitlink("a", short = FALSE) logitlink("a", short = FALSE, tag = TRUE) logofflink(1:5, offset = 1) # Same as log(1:5 + 1) powerlink(1:5, power = 2) # Same as (1:5)^2 # } # NOT RUN { # This is old and no longer works: logofflink(1:5, earg = list(offset = 1)) powerlink(1:5, earg = list(power = 2)) # } # NOT RUN { fit1 <- vgam(agaaus ~ altitude, binomialff(link = "clogloglink"), hunua) # best fit2 <- vgam(agaaus ~ altitude, binomialff(link = clogloglink ), hunua) # okay # } # NOT RUN { # This no longer works since "clog" is not a valid VGAM link function: fit3 <- vgam(agaaus ~ altitude, binomialff(link = "clog"), hunua) # not okay # No matter what the link, the estimated var-cov matrix is the same y <- rbeta(n = 1000, shape1 = exp(0), shape2 = exp(1)) fit1 <- vglm(y ~ 1, betaR(lshape1 = "identitylink", lshape2 = "identitylink"), trace = TRUE, crit = "coef") fit2 <- vglm(y ~ 1, betaR(lshape1 = logofflink(offset = 1.1), lshape2 = logofflink(offset = 1.1)), trace=TRUE) vcov(fit1, untransform = TRUE) vcov(fit1, untransform = TRUE) - vcov(fit2, untransform = TRUE) # Should be all 0s \dontrun{ # This is old: fit1@misc$earg # Some 'special' parameters fit2@misc$earg # Some 'special' parameters are here } par(mfrow = c(2, 2)) p <- seq(0.05, 0.95, len = 200) # A rather restricted range x <- seq(-4, 4, len = 200) plot(p, logitlink(p), type = "l", col = "blue") plot(x, logitlink(x, inverse = TRUE), type = "l", col = "blue") plot(p, logitlink(p, deriv=1), type="l", col="blue") # 1 / (p*(1-p)) plot(p, logitlink(p, deriv=2), type="l", col="blue") # (2*p-1)/(p*(1-p))^2 # }
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