Matrix functions

Furthermore, there are specific functions for matrices:

• The following function extracts the diagonal as a vector:

m<-matrix(c(1,2,3,4,5,6,7,8,9), nrow=3, ncol=3)
m
##      [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9
diag(m)
## [1] 1 5 9

• Returns the dimensions of a matrix:

dim(m)
## [1] 3 3

• Returns the sum of columns of a matrix:

colSums(m)
## [1]  6 15 24

• Returns the sum of rows of a matrix:

rowSums(m)
 ## [1] 12 15 18

• The transpose of a matrix can be obtained using the following code:

t(m)
##      [,1] [,2] [,3]
## [1,]    1    2    3
## [2,]    4    5    6
## [3,]    7    8    9

• Returns the determinant of a matrix:

det(m)
## [1] 0

• The auto-values and auto-vectors of a matrix are obtained using the following code:

eigen(m)
## eigen() decomposition
## $values
## [1]  1.611684e+01 -1.116844e+00 -5.700691e-16
##
## $vectors
##            [,1]       [,2]       [,3]
## [1,] -0.4645473 -0.8829060  0.4082483
## [2,] -0.5707955 -0.2395204 -0.8164966
## [3,] -0.6770438  0.4038651  0.4082483