# Returns a stratified sample without replacement

`sampleBy.Rd`

Returns a stratified sample without replacement based on the fraction given on each stratum.

## Usage

```
sampleBy(x, col, fractions, seed)
# S4 method for SparkDataFrame,character,list,numeric
sampleBy(x, col, fractions, seed)
```

## Arguments

- x
A SparkDataFrame

- col
column that defines strata

- fractions
A named list giving sampling fraction for each stratum. If a stratum is not specified, we treat its fraction as zero.

- seed
random seed

## See also

Other stat functions:
`approxQuantile()`

,
`corr()`

,
`cov()`

,
`crosstab()`

,
`freqItems()`

## Examples

```
if (FALSE) {
df <- read.json("/path/to/file.json")
sample <- sampleBy(df, "key", fractions, 36)
}
```