doBy (version 4.6.21)

by-sample: Sampling from a data frame

Description

A data frame is split according to some variables in a formula, and a sample of a certain fraction of each is drawn.

Usage

sample_by(data, formula, frac = 0.1, replace = FALSE, systematic = FALSE)
sampleBy(
  formula,
  frac = 0.1,
  replace = FALSE,
  data = parent.frame(),
  systematic = FALSE
)

Value

A dataframe.

Arguments

data

A data frame.

formula

A formula defining the grouping of the data frame.

frac

The part of data to be sampled.

replace

Is the sampling with replacement.

systematic

Should sampling be systematic.

Details

If systematic=FALSE (default) then frac gives the fraction of data sampled. If systematic=TRUE and frac=.2 then every 1/.2 i.e. every 5th observation is taken out.

See Also

orderBy, order_by, splitBy, split_by, summaryBy, summary_by, transformBy, transform_by

Examples

data(dietox)
sampleBy(formula = ~ Evit + Cu, frac=.1, data = dietox)