The **dim()** function in **R** is **“used to get or set the dimensions of a matrix, array, or data frame“**. For example, **dim(m)** returns the dimensions of **m**, and **dim(m) <- c(3, 4)** sets the dimensions for **m,** which has **3** rows and **4** columns.

**Syntax**

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

**Parameters**

**data:** It is an input R Object whose dimension we must get.

**Return value**

The dim() function returns NULL for a vector or a numeric vector for a **data** **frame, matrix,** or **array.**

**Example 1:Use the dim() function to get the dimensions of the Data Frame**

```
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.

The **‘dim()’** function returns the number of rows and columns as an integer vector for the data frame.

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]
```

**Example 2: ****Use dim() to set dimensions of Matrix**

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 to multi-dimensions using the dim() function.

**Example 3: ****Use dim() function to get dimensions of Matrix**

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
```

**Example 4: Use the dim() function to get the dimensions of the array**

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`

**Example 5: Use the dim() function to get the dimensions of the list**

If you try to use **dim()** on a list, you’ll likely get “**NULL”** because a list in R is not inherently multi-dimensional like a matrix or array.

```
list1 <- list(c(19, 21, 18), c(46, 50, 60))
dim(list1)
```

**Output**

```
NULL
```

**Example 6: Use the dim() function to get the dimensions of the vector**

A vector is a one-dimensional object and, thus, doesn’t have dimensions in the way that a matrix or array does. That’s why if you pass the vector to the dim() function, it returns **NULL.**

```
rv <- c(19, 21, 18)
dim(rv)
```

**Output**

`NULL`

That’s it.

Krunal Lathiya is a Software Engineer with over eight years of experience. He has developed a strong foundation in computer science principles and a passion for problem-solving. In addition, Krunal has excellent knowledge of Data Science and Machine Learning, and he is an expert in R Language.