Number of model parameters

This function returns the number of model parameters.

Usage

# S3 method for class 'maxim'
nParam(x, free=FALSE, ...)

Arguments

x

a model returned by a maximisation method from the maxLik package.

free

logical, whether to report only the free parameters or the total number of parameters (default)

...

other arguments for methods

Details

Free parameters are the parameters with no equality restrictions. Some parameters may be jointly restricted (e.g. sum of two probabilities equals unity). In this case the total number of parameters may depend on the normalization.

Value

Number of parameters in the model

Author

Ott Toomet

See also

nObs for number of observations

Examples

## fit a normal distribution by ML
# generate a variable from normally distributed random numbers
x <- rnorm( 100, 1, 2 )
# log likelihood function (for individual observations)
llf <- function( param ) {
   return( dnorm( x, mean = param[ 1 ], sd = param[ 2 ], log = TRUE ) )
}
## ML method
ml <- maxLik( llf, start = c( mu = 0, sigma = 1 ) )
# return number of parameters
nParam( ml )
#> [1] 2