locate.fid: Returns the index locations that match vector fid within data...

Description Usage Arguments Details Value Author(s) See Also Examples

View source: R/locate.fid.R

Description

Returns the index locations that match vector fid within data vector.

Usage

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locate.fid(fid, vect, long = TRUE)

Arguments

fid

A lookup vector, typically numeric, which can be 1 element long or greater. Typical use is 2 elements long. fid<-c(1,2). This sequence of values will be searched within the data vector, vect.

vect

Data vector of interest, within which fid will be searched.

long

Default is TRUE, will use a slower algorithm. When long=true, any length of fid can be used to search in vector. Computing time also depends on the length of fid. Caution advised when setting long = FALSE. Null values maye be returned.

Details

Returns the positions within the data vector where fid is found. Do not use this function if fid is length = 1. Use which(). If length(fid)>1, the elements of fid must be adjacent and in that specific order.

Value

An object of type integer, to be used as an index subset.

Author(s)

Glenn J. Tattersall

See Also

match which

Examples

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# Similar to the which or match functions in package::base, except that this returns the 
# index placement where variable fid occurs in data

## Define a vector
s<-c(2,3,42,38,88,33,55,99,32,56,22,48,1,2,3,5,6,7,8,9,10,12,20)
## Define what fid sequence to look for: i.e. what adjacent elements to look for in 
## this order
fid<-c(22,48)
## look for all instances where 22 and 48 occur together, using locate.fid
system.time(where.locate<-locate.fid(fid,s,long=FALSE))
where.locate
## verify that locate.fid worked by subsetting s, using where.locate as index
s[where.locate]
system.time(where.locate<-locate.fid(fid,s,long=TRUE))
s[where.locate]

## longer algorithm check
### Define a vector of 100000 random numbers from 1 to 100
s<-ceiling(runif(100000, 0, 100))
## Define what fid sequence to look for: i.e. what adjacent elements to look for in 
## this order
fid<-c(22,48)
system.time(where.locate<-locate.fid(fid,s,long=TRUE))
where.locate
## verify that locate.fid worked by subsetting s, using where.locate as index
s[where.locate]

Thermimage documentation built on Nov. 30, 2017, 9:01 a.m.