To find all unique combinations of two vectors in R, you can use two different functions **expand.grid()** and **crossing()** function from **tidyr** package.

The following methods show how you can do it with syntax.

**Method 1: Use expand.grid() Function**

```
expand.grid(vector1, vector2)
```

**Method 2: Use crossing() Function**

```
library(tidyr)
crossing(Temperature, Humidity)
```

The following examples show how to find all unique combination of two vector using **expand.grid()** and **crossing()** function in R.

## Using expand.grid() Function

Let’s see how we can use **expand.grid()** function in R:

```
# Define vectors
Machine=c("A","B","C","D")
Humidity=c(5,7,1,2)
# Find all unique combinations of Temperature and Humidity
u <- expand.grid(Machine,Humidity)
# Show combinations
print(u)
```

Output:

```
Var1 Var2
1 A 5
2 B 5
3 C 5
4 D 5
5 A 7
6 B 7
7 C 7
8 D 7
9 A 1
10 B 1
11 C 1
12 D 1
13 A 2
14 B 2
15 C 2
16 D 2
```

Here the output shows all unique combinations for **Machine** and **Humidity** vector.

## Using crossing() Function

Let’s see how we can use **crossing()** function from **tidyr** package in R:

```
# Import package
library(tidyr)
# Define vectors
Machine=c("A","B","C","D")
Humidity=c(5,7,1,2)
# Find all unique combinations of Temperature and Humidity
u <- crossing(Temperature, Humidity)
# Display all unique combinations of Temperature and Humidity
print(u)
```

Output:

```
Machine Humidity
<chr> <dbl>
1 A 1
2 A 2
3 A 5
4 A 7
5 B 1
6 B 2
7 B 5
8 B 7
9 C 1
10 C 2
11 C 5
12 C 7
13 D 1
14 D 2
15 D 5
16 D 7
```

Here the output shows all unique combinations of **Machine** and **Humidity** vector using **crossing()** function.