

- Trending Categories
Data Structure
Networking
RDBMS
Operating System
Java
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to find the index of n number of maximums in each row of a matrix in R?
If a matrix has multiple columns and values in each row are different then there will be number of maximums equal to the number of columns. Suppose, we want to extract the index of two maximums in each row in a matrix called M then we can use the below command −
t(apply(M,1,order,decreasing=TRUE)[1:2,])
Example1
> M1<-matrix(rpois(80,5),ncol=4) > M1
Output
[,1] [,2] [,3] [,4] [1,] 7 4 4 10 [2,] 7 1 4 3 [3,] 9 6 6 4 [4,] 6 5 3 3 [5,] 3 3 2 4 [6,] 5 6 2 2 [7,] 4 7 3 10 [8,] 6 0 11 6 [9,] 1 6 2 2 [10,] 4 9 4 9 [11,] 4 10 3 6 [12,] 3 9 3 11 [13,] 5 4 7 2 [14,] 6 7 6 6 [15,] 2 5 6 3 [16,] 2 5 8 2 [17,] 0 3 1 6 [18,] 6 10 6 4 [19,] 3 4 5 5 [20,] 4 5 8 4
Finding the index of two maximums in each of M1 −
> t(apply(M1,1,order,decreasing=TRUE)[1:2,])
Output
[,1] [,2] [1,] 4 1 [2,] 1 3 [3,] 1 2 [4,] 1 2 [5,] 4 1 [6,] 2 1 [7,] 4 2 [8,] 3 1 [9,] 2 3 [10,] 2 4 [11,] 2 4 [12,] 4 2 [13,] 3 1 [14,] 2 1 [15,] 3 2 [16,] 3 2 [17,] 4 2 [18,] 2 1 [19,] 3 4 [20,] 3 2
Example2
> M2<-matrix(rpois(80,50),ncol=4) > M2
Output
[,1] [,2] [,3] [,4] [1,] 65 52 42 63 [2,] 52 49 43 54 [3,] 50 35 49 57 [4,] 52 42 36 52 [5,] 48 36 45 43 [6,] 49 65 62 51 [7,] 52 46 56 51 [8,] 43 51 41 53 [9,] 53 40 51 55 [10,] 52 48 48 41 [11,] 54 44 48 42 [12,] 43 34 58 54 [13,] 41 50 51 45 [14,] 47 40 56 39 [15,] 49 48 42 38 [16,] 50 56 47 56 [17,] 55 48 39 52 [18,] 49 39 48 37 [19,] 53 49 58 50 [20,] 38 57 48 59
Finding the index of two maximums in each of M2 −
> t(apply(M2,1,order,decreasing=TRUE)[1:2,])
Output
[,1] [,2] [1,] 1 4 [2,] 4 1 [3,] 4 1 [4,] 1 4 [5,] 1 3 [6,] 2 3 [7,] 3 1 [8,] 4 2 [9,] 4 1 [10,] 1 2 [11,] 1 3 [12,] 3 4 [13,] 3 2 [14,] 3 1 [15,] 1 2 [16,] 2 4 [17,] 1 4 [18,] 1 3 [19,] 3 1 [20,] 4 2
- Related Questions & Answers
- Find the column index of least value for each row of an R matrix
- How to find the number of zeros in each column of a matrix in R?
- How to find the number of characters in each row of a string column in R?
- How to find the number of zeros in each row of a data.table object in R?
- How to find the row product of a matrix in R?
- How to find the number of zeros in each row of an R data frame?
- How to find the row-wise index of non-NA values in a matrix in R?
- How to find the variance of row elements of a matrix in R?
- How to add a vector to each row of a matrix in R?
- C++ program to find the Sum of each Row and each Column of a Matrix
- How to find the number of unique values in each row of an R data frame?
- How to find the row products for each row in an R matrix?
- How to find n number of quartiles for every row in R?
- How to find the row-wise mode of a matrix in R?
- How to find the percentage of zeros in each column of a matrix in R?
Advertisements