To create a list in R, use the list() method. But in some scenarios, we have to convert a list into a vector, and to do that, we can use the unlist() function. The

**unlist() function in R**

The unlist() function is used to convert a list to vector in R. The unlist() function takes the list as an argument and returns the Vector. It flattens the list.

**Syntax**

`unlist(list, recursive = TRUE, use.names = TRUE)`

**Parameters**

**list**: It is an R object, typically a list or vector.

**recursive**: It is a logical value that should unlist be applied to list components of x?

**use.names:** It is logical. Should names be preserved?

**Return Value**

The unlist() method returns a vector.

The output type is determined from the highest type of the components in the hierarchy NULL < raw < logical < integer < double < complex < character < list < expression, after coercion of pairlists to lists.

**Example**

The unlist() function converts a list of vectors into a single vector. Let’s define a list of vectors and pass that list to the unlist() function. To create a list in R, use the list() function.

```
data <- list(c(11, 18, 19, 21, 46))
class(data)
rv <- unlist(data)
rv
class(rv)
```

**Output**

```
[1] "list"
[1] 11 18 19 21 46
[1] "numeric"
```

As you can see, the unlist() function returns the vector, and in our case, it is a numeric vector.

**Unlist the List of Data Frames**

We can create a list that contains vector and data frame.

First, let’s define a list with two vectors.

```
data <- list(c(11, 18, 19, 21),
c(4, 10, 20, 46))
mix <- data
mix
```

Here, the data list only contains vectors. Nothing else.

Now, we will append a new list item, which will be a data frame. To create a data frame, use the data.frame() function.

To append an element to the list, use the double box brackets ( [[ ]] ).

```
mix[[3]] <- data.frame(x1 = c(5, 1, 2),
x2 = c(7, 5, 7))
```

Let’s see the mix list in the output.

```
data <- list(c(11, 18, 19, 21),
c(4, 10, 20, 46))
mix <- data
mix
cat("-------------------------", "\n")
cat("Modified list is: ", "\n")
cat("-------------------------", "\n")
mix[[3]] <- data.frame(x1 = c(5, 1, 2),
x2 = c(7, 5, 7))
mix
```

**Output**

```
[[1]]
[1] 11 18 19 21
[[2]]
[1] 4 10 20 46
-------------------------
Modified list is:
-------------------------
[[1]]
[1] 11 18 19 21
[[2]]
[1] 4 10 20 46
[[3]]
x1 x2
1 5 7
2 1 5
```

Now, use the unlist() function to unpack the list and print the elements one by one.

```
data <- list(c(11, 18, 19, 21),
c(4, 10, 20, 46))
mix <- data
mix
cat("-------------------------", "\n")
cat("Modified list is: ", "\n")
cat("-------------------------", "\n")
mix[[3]] <- data.frame(x1 = c(5, 1, 2),
x2 = c(7, 5, 7))
mix
cat("-------------------------", "\n")
cat("Unpacked list is: ", "\n")
cat("-------------------------", "\n")
unlist(mix)
```

**Output**

```
[[1]]
[1] 11 18 19 21
[[2]]
[1] 4 10 20 46
-------------------------
Modified list is:
-------------------------
[[1]]
[1] 11 18 19 21
[[2]]
[1] 4 10 20 46
[[3]]
x1 x2
1 5 7
2 1 5
3 2 7
-------------------------
Unpacked list is:
-------------------------
x11 x12 x13 x21 x22 x23
11 18 19 21 4 10 20 46 5 1 2 7 5 7
```

As you can see in the output that each column of the data matrix is unlisted itself.

**Convert data frame to vector**

To convert a data frame to vector in R, use the unlist() function.

```
rl <- unlist(BOD)
rl
```

**Output**

```
Time1 Time2 Time3 Time4 Time5 Time6 demand1 demand2 demand3 demand4
1.0 2.0 3.0 4.0 5.0 7.0 8.3 10.3 19.0 16.0
demand5 demand6
15.6 19.8
```

If you want just values and not column names, then you can pass the **use.names =** **FALSE**.

```
rl <- unlist(BOD, use.names = FALSE)
rl
```

**Output**

` [1] 1.0 2.0 3.0 4.0 5.0 7.0 8.3 10.3 19.0 16.0 15.6 19.8`

As you can see, we removed the names and print only the column values, and to do that, and we used **use.names = FALSE** as an argument to unlist() function.

## Unlist a list of character vectors in R

To unlist a character vector in R, use the unlist() function.

```
rs <- list(c("A", "B", "X", "Y"))
ul <- unlist(rs)
ul
```

**Output**

`[1] "A" "B" "X" "Y"`

That is it for the unlist() function in the R tutorial.

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.