# F.start.limits: Set starting values and limits for parameters of Rdistance... In Rdistance: Distance-Sampling Analyses for Density and Abundance Estimation

 F.start.limits R Documentation

## Set starting values and limits for parameters of Rdistance functions

### Description

Return reasonable starting values and limits (boundaries) for the parameters of distance functions. Starting values and limits are specified for all likelihoods and expansion terms. This function is called by other routines in `Rdistance`, and is not intended to be called by the user.

### Usage

``````F.start.limits(
like,
expan,
w.lo,
w.hi,
dist,
covars = NULL,
pointSurvey = FALSE
)
``````

### Arguments

 `like` String specifying the likelihood for the distance function. Possible values are "hazrate" for hazard rate likelihood, "halfnorm" for the half normal likelihood, "uniform" for the uniform likelihood, "negexp" for the negative exponential likelihood, and "Gamma" for the gamma likelihood. `expan` Number of expansion terms to include. Valid values are 0, 1, ..., 3. `w.lo` Lower or left-truncation limit of the distances. Normally, 0. `w.hi` Upper or right-truncation limit of the distances. This is the maximum off-transect distance that could be observed. `dist` The vector of observed off-transect distances being analyzed. This vector is only required for `like` = "Gamma" and "halfnorm". `covars` Matrix of covariate values. `pointSurvey` Boolean. TRUE if point transect data, FALSE if line transect data.

### Details

The number of parameters to be fitted is `expan + 1 + 1*(like %in% c("hazrate", "uniform"))`. This is the length of all vectors returned in the output list.

### Value

A list containing the following components

 `start` Vector of reasonable starting values for parameters of the likelihood and expansion terms. `lowlimit` Vector of lower limits for the likelihood parameters and expansion terms. `uplimit` Vector of upper limits for the likelihood parameters and expansion terms. `names` Vector of names for the likelihood parameters and expansion terms.

`dfuncEstim`

### Examples

``````  data(sparrowDetectionData)
dist <- sparrowDetectionData\$dist
units(dist) <- "m"
wl <- units::as_units(0, "m")
wh <- units::as_units(1000, "m")

F.start.limits("uniform", 0, wl, wh, dist)
F.start.limits("uniform", 1, wl, wh, dist)
F.start.limits("uniform", 2, wl, wh, dist)
F.start.limits("uniform", 3, wl, wh, dist)

F.start.limits("halfnorm", 0, wl, wh, dist)
F.start.limits("halfnorm", 1, wl, wh, dist)
F.start.limits("halfnorm", 2, wl, wh, dist)
F.start.limits("halfnorm", 3, wl, wh, dist)

F.start.limits("halfnorm", 0, wl, wh, dist, pointSurvey = TRUE)
F.start.limits("halfnorm", 1, wl, wh, dist, pointSurvey = TRUE)
F.start.limits("halfnorm", 2, wl, wh, dist, pointSurvey = TRUE)
F.start.limits("halfnorm", 3, wl, wh, dist, pointSurvey = TRUE)

F.start.limits("halfnorm", 0, wl, wh, dist, data.frame(A=1, B=2))
F.start.limits("halfnorm", 1, wl, wh, dist, data.frame(A=1, B=2))
F.start.limits("halfnorm", 2, wl, wh, dist, data.frame(A=1, B=2))
F.start.limits("halfnorm", 3, wl, wh, dist, data.frame(A=1, B=2))

F.start.limits("halfnorm", 0, wl, wh, dist, data.frame(A=1, B=2), TRUE)
F.start.limits("halfnorm", 1, wl, wh, dist, data.frame(A=1, B=2), TRUE)
F.start.limits("halfnorm", 2, wl, wh, dist, data.frame(A=1, B=2), TRUE)
F.start.limits("halfnorm", 3, wl, wh, dist, data.frame(A=1, B=2), TRUE)

F.start.limits("hazrate", 0, wl, wh, dist)
F.start.limits("hazrate", 1, wl, wh, dist)
F.start.limits("hazrate", 2, wl, wh, dist)
F.start.limits("hazrate", 3, wl, wh, dist)

F.start.limits("negexp", 0, wl, wh, dist)
F.start.limits("negexp", 1, wl, wh, dist)
F.start.limits("negexp", 2, wl, wh, dist)
F.start.limits("negexp", 3, wl, wh, dist)

F.start.limits("Gamma", 0, wl, wh, dist)
``````

Rdistance documentation built on July 9, 2023, 6:46 p.m.