# dim() in R: How to Get or Set Dimension of R Objects

The dim has a method for data frames, which returns the length of the row.names attribute of input data, and the length of input data is the numbers of “rows” and “columns”.

## dim() in R

The dim() is an inbuilt R function that either sets or returns the dimension of the matrix, array, or data frame. The dim() function takes the R object as an argument and returns its dimension, or if you assign the value to the dim() function, then it sets the dimension for that R Object.

### Syntax

``````# To get the dimension value
dim(data)

# To set the dimension value
dim(data) <- value``````

### Parameters

The data is an input R Object whose dimension we have to get.

If we want to assign a new dimension, then use the second syntax.

### Example

``````df <- data.frame(c1 = c("a", "b", "c", "d"),
c2 = c("e", "f", "g", "h"),
c3 = c("i", "j", "k", "l"),
c4 = c("m", "n", "o", "p"),
c5 = c("q", "r", "s", "t"))

df
cat("The dimension of data frame is: ", "\n")
dim(df)
``````

#### Output

``````   c1 c2 c3 c4 c5
1  a  e  i  m  q
2  b  f  j  n  r
3  c  g  k  o  s
4  d  h  l  p  t
The dimension of data frame is:
[1] 4 5``````

From the output, you can see that our data frame has (4, 5) dimensions. We have four rows and five columns.

For the data frame, the `dim()` function returns the number of rows and columns as an integer vector.

The functions dim() and dim<-  are generic.

The simple versions of nrow and ncol could be defined as follows.

``````nrow0 <- function(x) dim(x)[1]
ncol0 <- function(x) dim(x)[2]``````

## Find the dimension of Vector in R

To find the dimension of the Vector, use the dim() function. The dimension of the vector always returns NULL.

``````rv <- c("u", "v", "w", "x")
cat("The dimension of Vector is: ", "\n")
dim(rv)``````

#### Output

``````The dimension of Vector is:
NULL``````

And it returns NULL. The dimension of the Vector in R is NULL.

To get the number of elements of the Vector, use the length() function.

## Set dimension of a matrix in R

To set the dimension of the matrix, define a vector and use the dim() function to set the dimension.

``````rv <- rep(1:10)
rv

dim(rv) <- c(2, 5)
rv``````

#### Output

``````[1] 1 2 3 4 5 6 7 8 9 10
[,1] [,2] [,3] [,4] [,5]
[1,]  1    3   5    7     9
[2,]  2    4   6    8    10``````

We change the dimension from one dimension to multi-dimensions using the dim() function.

## How to find the dimension of Matrix in R

To get the dimension of the matrix in R, use the dim attribute of the object.

``````rv <- 1:6
mtrx <- matrix(rv, 3, 2)
mtrx
dim(mtrx)``````

#### Output

``````      [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6
[1] 3 2``````

## dim() of Array in R

To get the dimension of the array in R, use the dim() function.

``````arr <- array(1:24, dim = 2:4)
dim(arr)``````

#### Output

``[1] 2 3 4``

That is it for dim() function in the R Programming language.

Categories R