How to add a vector to each row of a matrix in R?

To add a vector to reach row of a matrix, we can use addition sign (+) and create the repetition of the vector up to the number of rows in the matrix. For example, if we have a matrix called M then a vector say v can be added to each row of M by using the command −

M+rep(v,each=nrow(M))

Example1

Consider the below matrix and the vector −

Live Demo

> M1<-matrix(rpois(40,2),nrow=20) > M1

Output

      [,1] [,2]  [1,]    3    2  [2,]    3    3  [3,]    4    2  [4,]    5    1  [5,]    3    1  [6,]    2    2  [7,]    1    2  [8,]    2    1  [9,]    3    2 [10,]    0    1 [11,]    3    4 [12,]    2    6 [13,]    3    1 [14,]    4    0 [15,]    1    3 [16,]    1    0 [17,]    1    1 [18,]    0    1 [19,]    1    3 [20,]    2    0

Adding v1 to rows in M1 −

> M1+rep(v1,each=nrow(M1))

Output

      [,1] [,2]  [1,]    4    3  [2,]    4    4  [3,]    5    3  [4,]    6    2  [5,]    4    2  [6,]    3    3  [7,]    2    3  [8,]    3    2  [9,]    4    3 [10,]    1    2 [11,]    4    5 [12,]    3    7 [13,]    4    2 [14,]    5    1 [15,]    2    4 [16,]    2    1 [17,]    2    2 [18,]    1    2 [19,]    2    4 [20,]    3    1

Example2

Live Demo

> M2<-matrix(rnorm(60),ncol=3) > M2

Output

             [,1]        [,2]        [,3]  [1,] -1.16459899  0.04276452 -0.38747561  [2,]  0.50198231  1.40818681  1.34047754  [3,] -0.83571273  0.15311835 -0.66026732  [4,] -1.04751005  0.68401101  0.36614494  [5,] -0.13906013 -0.08104307  1.58938567  [6,]  0.79923477  0.13871823  1.19483957  [7,] -0.70957734 -1.22610985  0.79431236  [8,] -0.61919335 -1.67900016  0.75673298  [9,]  0.02131366  0.59198453 -0.51860397 [10,] -0.92114971 -0.94043054 -0.66674705 [11,] -0.26933585  0.61537773  1.18988144 [12,]  2.11994998 -0.62014441 -0.97012363 [13,] -0.45798423  0.92096389  0.74603167 [14,] -0.51599135 -0.01450992 -1.84365984 [15,] -0.29866554  0.99900886 -0.55598877 [16,] -0.91226758 -1.63915166 -0.20200339 [17,]  0.40107684  1.79162856 -0.02759807 [18,]  0.44712300 -0.07322323 -0.15221520 [19,]  0.15838286 -1.50611267 -0.07117655 [20,]  0.53166819 -0.99748658 -0.54070065 > v2<-c(100,100,100)

Adding v2 to rows in M2 −

> M2+rep(v2,each=nrow(M2))

Output

           [,1]      [,2]      [,3]  [1,]  98.83540 100.04276  99.61252  [2,] 100.50198 101.40819 101.34048  [3,]  99.16429 100.15312  99.33973  [4,]  98.95249 100.68401 100.36614  [5,]  99.86094  99.91896 101.58939  [6,] 100.79923 100.13872 101.19484  [7,]  99.29042  98.77389 100.79431  [8,]  99.38081  98.32100 100.75673  [9,] 100.02131 100.59198  99.48140 [10,]  99.07885  99.05957  99.33325 [11,]  99.73066 100.61538 101.18988 [12,] 102.11995  99.37986  99.02988 [13,]  99.54202 100.92096 100.74603 [14,]  99.48401  99.98549  98.15634 [15,]  99.70133 100.99901  99.44401 [16,]  99.08773  98.36085  99.79800 [17,] 100.40108 101.79163  99.97240 [18,] 100.44712  99.92678  99.84778 [19,] 100.15838  98.49389  99.92882 [20,] 100.53167  99.00251  99.45930