# R Using which() Function to Get Matrix Index of Value (Example Code)

In this R tutorial you’ll learn how to find the index positions of certain elements in a matrix using the which() function.

## Creation of Example Data

my_data <- matrix(letters[1:6], ncol = 6, nrow = 4) # Constructing matrix in R my_data # Display example matrix in RStudio # [,1] [,2] [,3] [,4] [,5] [,6] # [1,] "a" "e" "c" "a" "e" "c" # [2,] "b" "f" "d" "b" "f" "d" # [3,] "c" "a" "e" "c" "a" "e" # [4,] "d" "b" "f" "d" "b" "f" |

my_data <- matrix(letters[1:6], ncol = 6, nrow = 4) # Constructing matrix in R my_data # Display example matrix in RStudio # [,1] [,2] [,3] [,4] [,5] [,6] # [1,] "a" "e" "c" "a" "e" "c" # [2,] "b" "f" "d" "b" "f" "d" # [3,] "c" "a" "e" "c" "a" "e" # [4,] "d" "b" "f" "d" "b" "f"

## Example: Get Row & Column Index Positions of Particular Value in Matrix

which(my_data == "a", arr.ind = TRUE) # Return position matrix # row col # [1,] 1 1 # [2,] 3 2 # [3,] 1 4 # [4,] 3 5 |

which(my_data == "a", arr.ind = TRUE) # Return position matrix # row col # [1,] 1 1 # [2,] 3 2 # [3,] 1 4 # [4,] 3 5

## Further Resources

In the following, you can find some additional resources on topics such as data inspection, vectors, indices, and variables.