Module # 6 Doing math in R part 2

 Answer the following questions and post your answer on your blog:

1. Consider A=matrix(c(2,0,1,3), ncol=2) and B=matrix(c(5,2,4,-1), ncol=2).
a) Find A + B
b) Find A - B

2. Using the diag() function to build a matrix of size 4 with the following values in the diagonal 4,1,2,3.

3. Generate the following matrix:

## [,1] [,2] [,3] [,4] [,5]
## [1,] 3 1 1 1 1
## [2,] 2 3 0 0 0
## [3,] 2 0 3 0 0
## [4,] 2 0 0 3 0
## [5,] 2 0 0 0 3



> # -----------------------------
> # Question 1: Matrix operations
> 
> A <- matrix(c(2, 0, 1, 3), ncol = 2)
> B <- matrix(c(5, 2, 4, -1), ncol = 2)
> 
> A
     [,1] [,2]
[1,]    2    1
[2,]    0    3
> B
     [,1] [,2]
[1,]    5    4
[2,]    2   -1
> 
> # a) A + B
> A_plus_B <- A + B
> A_plus_B
     [,1] [,2]
[1,]    7    5
[2,]    2    2
> 
> # b) A - B
> A_minus_B <- A - B
> A_minus_B
     [,1] [,2]
[1,]   -3   -3
[2,]   -2    4
> 
> # ---------------------------------------
> # Question 2: Diagonal matrix with diag()
> 
> D <- diag(c(4, 1, 2, 3))
> D
     [,1] [,2] [,3] [,4]
[1,]    4    0    0    0
[2,]    0    1    0    0
[3,]    0    0    2    0
[4,]    0    0    0    3
> 
> # ---------------------------------------
> # Question 3: Build the required matrix
> 
> M <- diag(3, 5)
> 
> M[1, ] <- c(3, 1, 1, 1, 1)
> 
> M[-1, 1] <- 2
> 
> M
     [,1] [,2] [,3] [,4] [,5]
[1,]    3    1    1    1    1
[2,]    2    3    0    0    0
[3,]    2    0    3    0    0
[4,]    2    0    0    3    0
[5,]    2    0    0    0    3

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