threeAFC {sensR} | R Documentation |
Creates af copy of the binomial family with the inverse link function changed to equal the 3-AFC psychometric function and correspondingly changed link function and derivative of the inverse link function.
threeAFC()
A binomial family object for models. Among other things it inludes the psychometric function as
linkinv
and the inverse psychometric function (for direct dprime computation) as
linkfun
.
Several functions in this package makes use of the function, but it may also be used on its own—see the example below.
Rune Haubo B Christensen and Per Bruun Brockhoff
Brockhoff, P.B. and Christensen, R.H.B. (2010). Thurstonian models for sensory discrimination tests as generalized linear models. Food Quality and Preference, 21, pp. 330-338.
triangle
, twoAFC
,
duotrio
, discrim
,
discrimPwr
, discrimSim
,
AnotA
, discrimSS
,
samediff
, findcr
xt <- matrix(c(10, 5), ncol = 2) # data: 10 correct answers, 5 incorrect res <- glm(xt ~ 1, family=threeAFC) summary(res) ## Extended example plotting the profile likelihood ## data: 10 correct answers, 5 incorrect xt <- matrix(c(10, 2), ncol = 2) summary(res <- glm(xt ~ 1, family = threeAFC))#, etastart = etastart)) N <- 100 dev <- double(N) level <- c(0.95, 0.99) delta <- seq(1e-4, 5, length = N) for(i in 1:N) dev[i] <- glm(xt ~ -1 + offset(delta[i]), family = threeAFC)$deviance plot(delta, exp(-dev/2), type = "l", xlab = expression(delta), ylab = "Normalized Profile Likelihood") ## Add Normal approximation: lines(delta, exp(-(delta - coef(res))^2 / (2 * vcov(res))), lty = 2) ## Add confidence limits: lim <- sapply(level, function(x) exp(-qchisq(x, df=1)/2) ) abline(h = lim, col = "grey")