R: Data Frames

data.frame {base} | R Documentation

## Data Frames

### Description

These functions create or manipulate data frames, tightly coupled collections of variables which share many of the properties of matrices and of lists, used as the fundamental data structure by most of R's modeling software.

### Usage

    data.frame(..., row.names = NULL, check.rows = FALSE,
            check.names = TRUE)

    as.data.frame(x, row.names = NULL, optional = FALSE)
    is.data.frame(x)

    row.names(x)
    row.names(x) <- names

### Arguments

`...` | these arguments are of either the form `value` or `tag=value`. Component names are created based on the tag (if present) or the deparsed argument itself.
`row.names` | a character vector giving the row names for the data frame.
`check.rows` | if `TRUE` then the rows are checked for consistency of length and names.
`check.names` | logical. If `TRUE` then the names of the variables in the data frame are checked to ensure that they are syntactically valid variable names. If necessary they are adjusted (by `make.names`) so that they are.
`optional` | logical. If `TRUE`, setting row names is optional.
`x` | object of class `data.frame`.

### Details

Character variables passed to `data.frame` are converted to factor columns unless protected by `I`. It also applies to adding columns to a data frame.

If a list or data frame or matrix is passed to `data.frame` it is as if each column had been passed as a separate argument, with the exception of matrices of class `model.matrix`.

### Value

For `data.frame(.)` a data frame, a matrix-like stucture whose columns may be of differing types (numeric, factor and character).
`as.data.frame` is generic function with many methods. It attempts to coerce its argument to be a data frame.
`is.data.frame` returns `TRUE` if its argument is a data frame and `FALSE` otherwise.
`row.names` can be used to set and retrieve the row names of a data frame, similarly to `rownames` for arrays (and it is a generic function that calls `rownames` for an array argument.

### Note

In versions of R prior to 1.4.0 (and in S3) logical columns were converted to factors.

### See Also

`print.data.frame`, `read.table`, `Math.data.frame` etc, about Group methods for `data.frame`s; `make.names`.

### Examples

    L3 <- LETTERS[1:3]
    str(d <- data.frame(cbind(x=1, y=1:10), fac=sample(L3, 10, repl=TRUE)))

    ## The same with automatic column names:
    str(     data.frame(cbind(  1,   1:10),     sample(L3, 10, repl=TRUE)))
    is.data.frame(d)

    ## do not convert to factor, using I() :
    str(cbind(d, char = I(letters[1:10])), vec.len = 10)

    stopifnot(1:10 == row.names(d))# {coercion}

    (d0  <- d[, FALSE]) # NULL dataframe with 10 rows
    (d.0 <- d[FALSE, ]) # <0 rows> dataframe  (3 cols)
    (d00 <- d0[FALSE,])  # NULL dataframe with 0 rows

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