R: Generate Factor Levels

gl {base} | R Documentation

## Generate Factor Levels

### Description

Generate factors by specifying the pattern of their levels.

### Usage

    gl(n, k, length = n*k, labels = 1:n, ordered = FALSE)

### Arguments

`n` | an integer giving the number of levels.
`k` | an integer giving the number of replications.
`length` | an integer giving the length of the result.
`labels` | an optional vector of labels for the resulting factor levels.
`ordered` | a logical indicating whether the result should be ordered or not.

### Value

The result has levels from `1` to `n` with each value replicated in groups of length `k` out to a total length of `length`.
`gl` is modelled on the GLIM function of the same name.

### See Also

The underlying `factor(.)`.

### Examples

    # First control, then treatment:
    gl(2,8, label=c("Control","Treat"))
    # 20 alternating 1s and 2s
    gl(2, 1, 20)
    # alternating pairs of 1s and 2s
    gl(2, 2, 20)

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