lab 2

1

i

ar<- matrix(c(10000,9000,11000,8000,7200,8800,4000,5000,6000),3,byrow=T,
          dimnames = list(c("A","B","C"),c("2019","2020","2021")))

pc <- matrix(c(2000,1800,2200,2400,1440,1760,1200,1500,2000),3,byrow=T,
           dimnames = list(c("A","B","C"),c("2019","2020","2021")))
# profit= ar-pc
profit<- ar-pc
apply(profit, 2, mean)

##     2019     2020     2021 
## 5466.667 5486.667 6613.333

ii

x<-c(-1,-2,-1,0,0,0,1,2,1,252,140,203,50,201,40,214,34,83,1,0,
     -1,2,0,-2,1,0,-1)

z<- array(x,dim = c(3,3,3))

z1<-z[,,1]
z2<-z[,,2]
z3<-z[,,3]

z1 %*% z2

##      [,1] [,2] [,3]
## [1,]  -49  -10 -131
## [2,]  -98  -20 -262
## [3,]  -49  -10 -131

z3 %*% z2

##      [,1] [,2] [,3]
## [1,]  735  492  365
## [2,]    0    0    0
## [3,] -735 -492 -365

2

m<- rbind(c(1,1,-1),c(4,0,1),c(0,4,1))
n <- cbind(c(0,8,16))

m_inverse <- solve(m)

answer <- m_inverse %*% n
answer

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