VGAM (version 0.9-6)

chisq: Chi-squared Distribution

Description

Maximum likelihood estimation of the degrees of freedom for a chi-squared distribution.

Usage

chisq(link = "loge", zero = NULL)

Arguments

link, zero

See CommonVGAMffArguments for information.

Value

• An object of class "vglmff" (see vglmff-class). The object is used by modelling functions such as vglm, and vgam.

Details

The degrees of freedom is treated as a parameter to be estimated, and as real (not integer). Being positive, a log link is used by default. Fisher scoring is used.

References

Forbes, C., Evans, M., Hastings, N. and Peacock, B. (2011) Statistical Distributions, Hoboken, NJ, USA: John Wiley and Sons, Fourth edition.

See Also

Chisquare. uninormal.

Examples

cdata <- data.frame(x2 = runif(nn <- 1000))
cdata <- transform(cdata, y1 = rchisq(nn, df = exp(1 - 1 * x2)),
                          y2 = rchisq(nn, df = exp(2 - 2 * x2)))
fit <- vglm(cbind(y1, y2) ~ x2, chisq, data = cdata, trace = TRUE)
coef(fit, matrix = TRUE)