Logistic and Inverse logistic functions
Inverse-logit function, transforms continuous values to the range (0, 1)
logit(x) invlogit(x)
x |
A vector of continuous values |
The Inverse-logit function defined as: logit^-1(x) = e^x/(1+e^x) transforms continuous values to the range (0, 1), which is necessary, since probabilities must be between 0 and 1 and maps from the linear predictor to the probabilities
A vector of estimated probabilities
Andrew Gelman gelman@stat.columbia.edu, M.Grazia Pittau grazia@stat.columbia.edu
Andrew Gelman and Jennifer Hill. (2006). Data Analysis Using Regression and Multilevel/Hierarchical Models. Cambridge University Press.
data(frisk) n <- 100 x1 <- rnorm (n) x2 <- rbinom (n, 1, .5) b0 <- 1 b1 <- 1.5 b2 <- 2 Inv.logit <- invlogit(b0+b1*x1+b2*x2) plot(b0+b1*x1+b2*x2, Inv.logit)
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