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%- Also NEED an '\alias' for EACH other topic documented here.
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\title{ Exponential Link Function }
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Computes the exponential transformation, including its inverse and the
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explink(theta, earg = list(), inverse = FALSE, deriv = 0, short = TRUE, tag = FALSE)
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%- maybe also 'usage' for other objects documented here.
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See below for further details.
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See \code{\link{Links}} for general information about \code{earg}.
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Logical. If \code{TRUE} the inverse function is computed.
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The inverse function is the \code{\link{loge}} function.
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Order of the derivative. Integer with value 0, 1 or 2.
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Used for labelling the \code{blurb} slot of a
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\code{\link{vglmff-class}} object.
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Used for labelling the linear/additive predictor in the
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\code{initialize} slot of a \code{\link{vglmff-class}} object.
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Contains a little more information if \code{TRUE}.
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The exponential link function is potentially suitable for parameters that
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Numerical values of \code{theta} close to negative or positive infinity
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\code{0}, \code{Inf}, \code{-Inf}, \code{NA} or \code{NaN}.
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The arguments \code{short} and \code{tag} are used only if
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\code{theta} is character.
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For \code{explink} with \code{deriv = 0}, the exponential of \code{theta}, i.e.,
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\code{exp(theta)} when \code{inverse = FALSE}.
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And if \code{inverse = TRUE} then
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if \code{theta} is not positive then it will return \code{NaN}.
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For \code{deriv = 1}, then the function returns
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\emph{d} \code{theta} / \emph{d} \code{eta} as a function of \code{theta}
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if \code{inverse = FALSE},
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else if \code{inverse = TRUE} then it returns the reciprocal.
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Here, all logarithms are natural logarithms, i.e., to base \emph{e}.
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% McCullagh, P. and Nelder, J. A. (1989)
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% \emph{Generalized Linear Models}, 2nd ed. London: Chapman & Hall.
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\author{ Thomas W. Yee }
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This function has particular use for computing quasi-variances when
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used with \code{\link{rcam}} and \code{\link{normal1}}.
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Numerical instability may occur when \code{theta} is
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close to negative or positive infinity.
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One way of overcoming this (one day) is to use \code{earg}.
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\code{\link{normal1}}.
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max(abs(explink(explink(theta), inverse = TRUE) - theta)) # Should be 0