replications {base} | R Documentation

## Number of Replications of Terms

### Description

Returns a vector or a list of the number of replicates for each term in the formula.

### Usage

    replications(formula, data=NULL, na.action)

### Arguments

`formula` | a formula or a terms object or a data frame.
`data` | a data frame used to find the objects in `formula`.
`na.action` | function for handling missing values. Defaults to a `na.action` attribute of `data`, then a setting of the option `na.action`, or `na.fail` if that is not set.

### Details

If `formula` is a data frame and `data` is missing, `formula` is used for `data` with the formula `~ .`.

### Value

A vector or list with one entry for each term in the formula giving the number(s) of replications for each level. If all levels are balanced (have the same number of replications) the result is a vector, otherwise it is a list with a component for each terms, as a vector, matrix or array as required.

A test for balance is `!is.list(replications(formula,data))`.

### Author(s)

B. D. Ripley

### See Also

`model.tables`

### Examples

    ## From Venables and Ripley (1997) p.210.
    N <- c(0,1,0,1,1,1,0,0,0,1,1,0,1,1,0,0,1,0,1,0,1,1,0,0)
    P <- c(1,1,0,0,0,1,0,1,1,1,0,0,0,1,0,1,1,0,0,1,0,1,1,0)
    K <- c(1,0,0,1,0,1,1,0,0,1,0,1,0,1,1,0,0,0,1,1,1,0,1,0)
    yield <- c(49.5,62.8,46.8,57.0,59.8,58.5,55.5,56.0,62.8,55.8,69.5,
    55.0, 62.0,48.8,45.5,44.2,52.0,51.5,49.8,48.8,57.2,59.0,53.2,56.0)

    npk <- data.frame(block=gl(6,4), N=factor(N), P=factor(P),
                      K=factor(K), yield=yield)
    replications(~ . - yield, npk)

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