secr (version 2.9.0)

snip: Slice Transect Into Shorter Sections

Description

This function splits the transects in a `transect' or `transectX' traps object into multiple shorter sections. The function may also be applied directly to a capthist object based on transect data. This makes it easy to convert detection data collected along linear transects to point detection data (see Example).

Usage

snip(object, from = 0, by = 1000, length.out = NULL, keep.incomplete = TRUE)

Arguments

object

secr `traps' or `capthist' object based on transects

from

numeric starting posiiton (m)

by

numeric length of new transects (m)

length.out

numeric number of new transects, as alternative to `by'

keep.incomplete

logical; if TRUE then initial or terminal sections of each original transect that are less than `by' will be retained in the output

Value

• A `traps' or `capthist' object, according to the input. If keep.incomplete == FALSE animals and detections from the

Details

If a positive length.out is specified, by will be computed as (transectlength(object) - from) / length.out.

See Also

transectlength

Examples

x <- seq(0, 4*pi, length = 41)
temptrans <- make.transect(x = x*100, y = sin(x)*300, )
plot (snip(temptrans, by = 200), markvertices = 1)

## simulate some captures
tempcapt <- sim.capthist(temptrans, popn = list(D = 2,
   buffer = 300), detectpar = list(g0 = 0.5, sigma = 50),
   binomN = 0)

## snip capture histories
tempCH <- snip(tempcapt, by = 20)

## collapse from 'transect' to 'multi', discarding location within transects
tempCH <- reduce(tempCH, outputdetector = "count")

## fit secr model and examine H-T estimates of density
derived(secr.fit(tempCH, buffer = 300, CL = TRUE, trace = FALSE))

## also, may split an existing transect into equal lengths
## same result:
plot(snip(temptrans, by = transectlength(temptrans)/10),
    markvertices = 1)
plot(snip(temptrans, length.out = 10), markvertices = 1)