bigsample {ff} | R Documentation |
Sampling from large pools
Description
bigsample
samples quicker from large pools than sample
does.
Usage
bigsample(x, ...)
## Default S3 method:
bigsample(x, size, replace = FALSE, prob = NULL, negative = FALSE, ...)
## S3 method for class 'ff'
bigsample(x, size, replace = FALSE, prob = NULL, ...)
Arguments
x |
the pool to sample from |
size |
the number of elements to sample |
replace |
TRUE to use sampling with replacement |
prob |
optional vector of sampling probabilities (recyled to pool length) |
negative |
|
... |
|
Details
For small pools sample
is called.
Value
a vector of elements sampled from the pool (argument 'x')
Note
Note that bigsample
and sample
do not necessarily return the same sequence of elements when set.seed
is set before.
Author(s)
Daniel Adler, Jens Oehlschlägel, Walter Zucchini
See Also
Examples
message("Specify pool size")
bigsample(1e8, 10)
message("Sample ff elements (same as x[bigsample(length(ff(1:100 / 10)), 10)])")
bigsample(ff(1:100 / 10), 10)
## Not run:
message("Speed factor")
(system.time(for(i in 1:10)sample(1e8, 10))[3]/10)
/ (system.time(for(i in 1:1000)bigsample(1e8, 10))[3]/1000)
## End(Not run)
[Package ff version 4.0.12 Index]