subset.traps: Subset traps Object

Description

Retain selected rows of a traps object.

Usage

# S3 method for traps
subset(x, subset = NULL, occasions = NULL, …)
# S3 method for traps
split(x, f, drop = FALSE, prefix = "S", byoccasion = FALSE, …)

Arguments

traps object

subset

vector to subscript the rows of x

occasions

vector to subscript columns in usage(x)

…

arguments passed to other functions

factor or object that may be coerced to a factor

drop

logical indicating if levels that do not occur should be dropped (if f is a factor)

prefix

a character prefix to be used for component names when values of f are numeric

byoccasion

logical ; if TRUE then f is used to split occasions

Value

An object of class traps with only the requested subset of rows. Subsetting is applied to usage and covariates attributes if these are present.

Splitting with byoccasion = TRUE produces a list of traps objects, each with usage codes for a subset of occasions. Traps not used on any occasion within a session are automatically dropped from that session.

Details

The subscripts in subset may be of type integer, character or logical as described in Extract. By default, all rows are retained.

In the case of `polygon' and `transect' detectors, subsetting is done at the level of whole polygons or transects. subset should therefore have the same length as levels(polyID(x)) or levels(transectID(x)).

split generates a list in which each component is a traps object. Each component corresponds to a level of f. The argument x of split cannot be a list (i.e. x must be a single-session traps object).

If the levels of f are numeric, from version 2.10.3 a leading zero is inserted in the names of the output list to maintain the sort order.

Examples

Run this code

## odd-numbered traps only, using modulo operator
temptrap <- make.grid(nx = 7, ny = 7)
t2 <- subset(temptrap, as.logical(1:nrow(temptrap) %% 2))
plot(t2)

## this works also for even number of rows, but must change 'outer' call
temptrap <- make.grid(nx = 8, ny = 8)
t3 <- subset(temptrap, !as.logical(outer(1:8,1:8,'+')%%2))
plot(t3)