# nlFitStart: Find Starting Values for Fitting a Normal Laplace... In NormalLaplace: The Normal Laplace Distribution

 nlFitStart R Documentation

## Find Starting Values for Fitting a Normal Laplace Distribution

### Description

Finds starting values for input to a maximum likelihood routine for fitting a normal Laplace distribution to data.

### Usage

``````  nlFitStart(x, breaks = "FD",
paramStart = NULL,
startValues = c("MoM", "US"),
startMethodMoM = "Nelder-Mead", ...)
nlFitStartMoM(x, startMethodMoM = "Nelder-Mead", ...)
``````

### Arguments

 `x` Data vector. `breaks` Breaks for histogram. If missing, defaults to those generated by `hist(x, right = FALSE, plot = FALSE)`. `paramStart` Starting values for parameter vector if `startValues = "US"`. `startValues` Vector of the different starting value methods to consider. See Details. `startMethodMoM` Method used by call to `optim` in finding method of moments estimates. `...` Passes arguments to `optim`.

### Details

Possible values of the argument `startValues` are the following:

`"US"`

User-supplied.

`"MoM"`

Method of moments.

If `startValues = "US"` then a value must be supplied for `paramStart`.

If `startValues = "MoM"`, `nlFitStartMoM` is called.

If `startValues = "MoM"` an initial optimisation is needed to find the starting values. These optimisations call `optim`.

### Value

`nlFitStart` returns a list with components:

 `paramStart` A vector with elements `mu`, `sigma`, `alpha` and `beta` giving the starting value of param. `xName` A character string with the actual `x` argument name. `breaks` The cell boundaries found by a call to `hist`. `midpoints` The cell midpoints found by a call to `hist`. `empDens` The estimated density found by a call to `hist`.

`nlFitStartMoM` returns only the method of moments estimates as a vector with elements `mu`, `sigma`, `alpha` and `beta`.

### Author(s)

David Scott d.scott@auckland.ac.nz, Simon Potter

`dnl`, `nlFit`, `hist`, and `optim`.
``````param <- c(2, 2, 1, 1)