R: Sampling from a data frame

by-sample {doBy} | R Documentation

## 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
    )

### 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.

### Value

A dataframe.

### See Also

`summaryBy`, `orderBy`, `splitBy`, `transformBy`

### Examples

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

[Package doBy version 4.6.6 Index]