simplex {VGAM} | R Documentation

## Simplex distribution

### Description

The two parameters of the univariate simplex distribution are estimated.

### Usage

    simplex(lmu = "logit", lsigma = "loge",
            emu=list(), esigma=list(),
            imu = NULL, isigma = NULL)

### Arguments

`lmu` | Link function for `mu`. See `Links` for more choices. The parameter lies in the unit interval.
`lsigma` | Link function for `sigma`. See `Links` for more choices. The parameter is positive, therefore the log link is the default.
`emu, esigma` | List. Extra argument for each of the links. See `earg` in `Links` for general information.
`imu, isigma` | Optional initial values for `mu` and `sigma`. A `NULL` means a value is obtained internally.

### Details

See Jorgensen (1997) for details.

### Value

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

### Note

This distribution is potentially useful for dispersion modelling. This family function only works for intercept-only models, i.e., the formula should have `~ 1`.

### Author(s)

T. W. Yee

### References

Jorgensen, B. (1997) The Theory of Dispersion Models. London: Chapman & Hall

### See Also

`rig`.

### Examples

    x = runif(n <- 100)
    y = rbeta(n, shape1=3+x, shape2=4-x)
    (fit = vglm(y ~ 1, simplex, trace=TRUE, cri="coef"))
    coef(fit, matrix=TRUE)
    Coef(fit)
    summary(fit)

[Package VGAM version 0.7-9 Index]