# Select Data Frame Rows based on Values in Vector in R (4 Examples)

In this tutorial, Iâ€™ll explain how to extract certain rows according to the values in a vector in the R programming language.

Youâ€™re here for the answer, so letâ€™s get straight to the R syntaxâ€¦

## Creation of Example Data

As a first step, letâ€™s define some example data in R:

```data <- data.frame(x1 = 1:10,       # Create example data
x2 = letters[1:10])
data                                # Return example data
#    x1 x2
# 1   1  a
# 2   2  b
# 3   3  c
# 4   4  d
# 5   5  e
# 6   6  f
# 7   7  g
# 8   8  h
# 9   9  i
# 10 10  j```

Have a look at the previous RStudio console output. It shows that our example data frame has ten rows and two columns. The first variable is numeric and ranges from 1 to 10 and the second variable has the character class and ranges from the letter a to the letter j.

For this example, we also need to create a vector in R:

```vec <- c(1, 7, 10)                  # Create example vector
vec                                 # Return example vector
# 1  7 10```

Our vector has a length of three and consists of the numeric values 1, 7, and 10.

## Example 1: Extract Rows Using %in%-Operator

In Example 1, Iâ€™ll show how to use the %in%-operator to extract all rows from our data frame where the values of the variable x1 are contained in our example vector.

Have a look at the following R code:

```data[data\$x1 %in% vec, ]            # Applying %in%-operator
#    x1 x2
# 1   1  a
# 7   7  g
# 10 10  j```

Three rows of our data frame matched with the values of our vector, i.e. the filtered data frame consists of three rows.

## Example 2: Extract Rows Using is.element Function

This Example illustrates how to use the is.element function to select specific data frame rows based on the values of a vector object. Within the is.element function, we have to specify the column of our data and the name of our vector:

```data[is.element(data\$x1, vec), ]    # Applying is.element function
#    x1 x2
# 1   1  a
# 7   7  g
# 10 10  j```

As you can see based on the previous output of the RStudio console, the result of Examples 1 and 2 is exactly the same.

## Example 3: Extract Rows Using filter Function of dplyr Package

So far, we have only used the basic installation of the R programming language. However, a very popular add-on package for data manipulation is the dplyr package.

This Example shows how to use the dplyr package to select certain rows of a data frame according to the values in a vector (or array). In case we want to use the functions of the dplyr package, we first have to install and load dplyr:

```install.packages("dplyr")           # Install & load dplyr
library("dplyr")```

Now, we can apply the filter function of the dplyr package as shown below:

```filter(data, x1 %in% vec)           # Applying filter function
#   x1 x2
# 1  1  a
# 2  7  g
# 3 10  j```

Again, the same output!

## Example 4: Extract Rows Using setDT Function of data.table Package

Another popular add-on package for data manipulation is the data.table package. In Example 4, Iâ€™ll explain how to use the setDT and J functions to return specific rows of our data.

Again, we have to install and load the data.table package first:

```install.packages("data.table")      # Install & load data.table
library("data.table")```

Now, we can use the functions of the data.table package as follows:

```setDT(data, key = "x1")[J(vec)]     # Applying setDT function
#    x1 x2
# 1:  1  a
# 2:  7  g
# 3: 10  j```

The output is the same. However, the data.table package illustrates the returned data table with : in front of the data cells.

## Video, Further Resources & Summary

Do you need more info on the R programming code of the present article? Then I can recommend watching the following video of the Statistics Globe YouTube channel. Iâ€™m explaining the examples of this article in the video instruction:

Furthermore, I can recommend reading the related tutorials of my website. Some articles are shown here:

To summarize: In this R tutorial you learned how to select specific row items of a data frame using logical criteria based on vector elements. In case you have any additional questions, please let me know in the comments section below.

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