# dim

##### 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.frame`

s, 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.

##### See Also

##### 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 3.4.0, License: Part of R 3.4.0*

### 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 ```