sample2: A wrapper for 'sample.int' and 'extract' that makes it easy...

In grr: Alternative Implementations of Base R Functions

Description

Row names are not preserved.

Usage

sample2(x, size, replace = FALSE, prob = NULL)

Arguments

x	object from which to extract elements
size	a positive number, the number of items to choose.
replace	Should sampling be with replacement?
prob	A vector of probability weights for obtaining the elements of the vector being sampled.

Examples

#Sampling from a list
l1<-as.list(1:1e6)
b<-sample2(l1,1e5)

#Sampling from a data frame
orders<-data.frame(orderNum=sample(1e5, 1e6, TRUE),
   sku=sample(1e3, 1e6, TRUE),
   customer=sample(1e4,1e6,TRUE),stringsAsFactors=FALSE)
   
a<-sample2(orders,250000) 

#With oversampling sample2 can be much faster than the alternatives,
#with the caveat that it does not preserve row names.
system.time(a<-sample2(orders,2000000,TRUE))
system.time(b<-orders[sample.int(nrow(orders),2000000,TRUE),])
## Not run: 

system.time(c<-dplyr::sample_n(orders,2000000,replace=TRUE))

#Can quickly sample for sparse matrices while preserving sparsity
sm<-rsparsematrix(20000000,10000,density=.0001)
sm2<-sample2(sm,1000000)

## End(Not run)

grr documentation built on May 2, 2019, 5:57 a.m.