subset.traps  R Documentation 
Retain selected rows of a traps object.
## S3 method for class 'traps'
subset(x, subset = NULL, occasions = NULL, ...)
## S3 method for class 'traps'
split(x, f, drop = FALSE, prefix = "S", byoccasion = FALSE, ...)
x 

subset 
vector to subscript the rows of 
occasions 
vector to subscript columns in 
... 
arguments passed to other functions or to optional subset function (subset.traps) 
f 
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 
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
singlesession 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.
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.
split.traps
does not work for mark–resight data.
traps
,
rbind.traps
## oddnumbered 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)
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