Description Usage Arguments Details Value Warning Author(s) References See Also Examples

Maximum likelihood estimation of the (2-parameter) F distribution.

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`link` |
Parameter link function for both parameters.
See |

`idf1, idf2` |
Numeric and positive. Initial value for the parameters. The default is to choose each value internally. |

`nsimEIM, zero` |
See |

`imethod` |
Initialization method. Either the value 1 or 2.
If both fail try setting values for |

The F distribution is named after Fisher and has a density function
that has two parameters, called `df1`

and `df2`

here.
This function treats these degrees of freedom as *positive reals*
rather than integers.
The mean of the distribution is
*df2/(df2-2)* provided *df2>2*,
and its variance is
*2*df2^2*(df1+df2-2)/
(df1*(df2-2)^2*(df2-4))* provided *df2>4*.
The estimated mean is returned as the fitted values.
Although the F distribution can be defined to accommodate a
non-centrality parameter `ncp`

, it is assumed zero here.
Actually it shouldn't be too difficult to handle any known
`ncp`

; something to do in the short future.

An object of class `"vglmff"`

(see `vglmff-class`

).
The object is used by modelling functions such as `vglm`

and `vgam`

.

Numerical problems will occur when the estimates of the parameters are too low or too high.

T. W. Yee

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

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