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How to find the row means for each matrix stored in an R list?
To find the row mean of all matrices stored in an R list, we can use sapply function along with rowMeans function.
For example, if we have a list called LIST that contains some matrices then the row means for each matrix can be found by using the following command −
sapply(LIST,rowMeans)
Check out the below example to understand how it works.
Example
Following snippet creates the matrices −
M1<-matrix(rpois(40,2),ncol=2) M2<-matrix(rpois(40,2),ncol=2) M3<-matrix(rpois(40,5),ncol=2) List<-list(M1,M2,M3) List
output
The following matrices are created −
[[1]] [,1] [,2] [1,] 3 1 [2,] 4 0 [3,] 3 0 [4,] 3 0 [5,] 5 2 [6,] 3 2 [7,] 3 2 [8,] 3 2 [9,] 0 1 [10,] 1 3 [11,] 3 3 [12,] 1 1 [13,] 1 0 [14,] 1 2 [15,] 2 2 [16,] 4 3 [17,] 0 3 [18,] 0 1 [19,] 4 2 [20,] 4 2 [[2]] [,1] [,2] [1,] 4 3 [2,] 2 0 [3,] 2 0 [4,] 2 2 [5,] 3 2 [6,] 0 2 [7,] 2 1 [8,] 0 1 [9,] 3 1 [10,] 2 0 [11,] 4 1 [12,] 3 3 [13,] 4 1 [14,] 7 3 [15,] 3 2 [16,] 5 2 [17,] 2 4 [18,] 3 1 [19,] 1 3 [20,] 2 2 [[3]] [,1] [,2] [1,] 3 9 [2,] 3 8 [3,] 11 9 [4,] 2 3 [5,] 3 4 [6,] 5 6 [7,] 9 4 [8,] 4 4 [9,] 2 3 [10,] 7 6 [11,] 6 6 [12,] 2 6 [13,] 3 4 [14,] 4 1 [15,] 8 6 [16,] 3 11 [17,] 5 4 [18,] 6 4 [19,] 7 6 [20,] 8 7
Now, in order to find the row means for each matrix in List, add the following code to the above snippet −
Example
sapply(List,rowMeans)
Output
If you execute all the above given snippets as a single program, it generates the following Output −
[,1] [,2] [,3] [1,] 2.0 3.5 6.0 [2,] 2.0 1.0 5.5 [3,] 1.5 1.0 10.0 [4,] 1.5 2.0 2.5 [5,] 3.5 2.5 3.5 [6,] 2.5 1.0 5.5 [7,] 2.5 1.5 6.5 [8,] 2.5 0.5 4.0 [9,] 0.5 2.0 2.5 [10,] 2.0 1.0 6.5 [11,] 3.0 2.5 6.0 [12,] 1.0 3.0 4.0 [13,] 0.5 2.5 3.5 [14,] 1.5 5.0 2.5 [15,] 2.0 2.5 7.0 [16,] 3.5 3.5 7.0 [17,] 1.5 3.0 4.5 [18,] 0.5 2.0 5.0 [19,] 3.0 2.0 6.5 [20,] 3.0 2.0 7.5
Updated on: 02-Nov-2021
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