dim

From base v3.3 by R-core R-core@R-project.org

Dimensions of an Object

Retrieve or set the dimension of an object.

Keywords: array

Usage

dim(x)
dim(x) <- value

Arguments

x: an R object, for example a matrix, array or data frame.
value: For the default method, either NULL or a numeric vector, which is coerced to integer (by truncation).

Details

The functions dim and dim<- are internal generic primitive functions.

dim has a method for data.frames, which returns the lengths of the row.names attribute of x and of x (as the numbers of rows and columns respectively).

Value

For an array (and hence in particular, for a matrix) dim retrieves the dim attribute of the object. It is NULL or a vector of mode integer.The replacement method changes the "dim" attribute (provided the new value is compatible) and removes any "dimnames" and "names" attributes.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Examples

library(base)

x <- 1:12 ; dim(x) <- c(3,4)
x

# simple versions of nrow and ncol could be defined as follows
nrow0 <- function(x) dim(x)[1]
ncol0 <- function(x) dim(x)[2]

Documentation reproduced from package base, version 3.3, License: Part of R @VERSION@

Community examples

richie@datacamp.com at Jan 17, 2017 base v3.3.2

For matrices, `dim()` returns the number of rows and columns as an integer vector. ```{r} m <- matrix(1:12, 3, 4) dim(m) # 3 4 ``` The same is true for data frames. ```{r} d <- data.frame(a = 1:3, b = 4:6, c = 7:9, d = 10:12) dim(d) # 3 4 ``` For arrays, `dim()` can be longer than 2 values. ```{r} a <- array(1:24, dim = 2:4) dim(a) # 2 3 4 ``` Vectors don't have a dimension attribute; `dim()` will always return `NULL`. ```{r} v <- 1:12 dim(v) # NULL ```

dim