Table of Contents
You can use the following methods to replace specific values in a matrix in R:
Method 1: Replace Elements Equal to Specific Value
#replace 5 with 100 my_matrix[my_matrix==5] <- 100
Method 2: Replace Elements Based on One Condition
#replace elements with value less than 15 with 0 my_matrix[my_matrix<15] <- 0
Method 3: Replace Elements Based on Multiple Conditions
#replace elements with value between 10 and 15 with 99 my_matrix[my_matrix>=10 & my_matrix<=15] <- 99
The following examples show how to use each method in practice with the following matrix in R:
#create matrix my_matrix <- matrix(1:20, nrow = 5) #display matrix my_matrix [,1] [,2] [,3] [,4] [1,] 1 6 11 16 [2,] 2 7 12 17 [3,] 3 8 13 18 [4,] 4 9 14 19 [5,] 5 10 15 20
Example 1: Replace Elements Equal to Specific Value
The following code shows how to replace all elements equal to the value 5 with the value 100:
#replace 5 with 100 my_matrix[my_matrix==5] <- 100 #view updated matrix my_matrix [,1] [,2] [,3] [,4] [1,] 1 6 11 16 [2,] 2 7 12 17 [3,] 3 8 13 18 [4,] 4 9 14 19 [5,] 100 10 15 20
Notice that the one element equal to the value 5 has been replaced with a value of 100.
All other elements remained unchanged in the matrix.
Example 2: Replace Elements Based on One Condition
The following code shows how to replace all elements that have a value less than 15 with the value 0:
#replace elements with value less than 15 with 100 my_matrix[my_matrix<15] <- 0 #view updated matrix my_matrix [,1] [,2] [,3] [,4] [1,] 0 0 0 16 [2,] 0 0 0 17 [3,] 0 0 0 18 [4,] 0 0 0 19 [5,] 0 0 15 20
Example 3: Replace Elements Based on Multiple Conditions
The following code shows how to replace all elements that have a value between 10 and 15 with a value of 99:
#replace elements with value between 10 and 15 with 99 my_matrix[my_matrix>=10 & my_matrix<=15] <- 99 #view updated matrix my_matrix [,1] [,2] [,3] [,4] [1,] 1 6 99 16 [2,] 2 7 99 17 [3,] 3 8 99 18 [4,] 4 9 99 19 [5,] 5 99 99 20
Notice that each of the elements that have a value between 10 and 15 have been replaced with a value of 99.
The following tutorials explain how to perform other common tasks in R: