统计建模与R软件第二章习题答案

# 2.1
x <- c(1,2,3);y <- c(4,5,6)
e <- c(1,1,1)
#1)
z <- 2*x+y+e;z
#2)
crossprod(x,y)
#3)
outer(x,y)

#2.2
#按列输入（默认）
A <- matrix(1:20,c(4,5))
#按行输入
B <- matrix(1:20,c(4,5),byrow = TRUE)
#1)
C <- A+B;C
#2)
D <- A*B;D
#3)
#4)
A[1:3,1:3]
#5)
G <- B[,-3]

#2.3
x <- c(rep(1,5),rep(3,4),rep(4,2));x

#2.4
#1)
Hilbert <- function(n){
  H <- matrix(,n,n)
  for(i in 1:n){
    for(j in 1:n){
      H[i,j] = 1/(i+j-1)
    }
  }
  return(H)
}

#1)
Hilbert(5)
#2)
solve(Hilbert(5))
#3)
eigen(Hilbert(5))

#2.5
#2.7
fun <- function(n){
  if (n <= 0) {
    print("Insert positive number !");break}
  while (n != 1){
    if(n %% 2 == 0){n = n/2}
      else{n = 3*n+1}
    if (n == 1) print("success!")
  }
}

# v2
fun_1 <- function(n){
  if (n <= 0) {
    print("Insert positive number !");break}
  while (n != 1){
    if(n %% 2 == 0){n = n/2}
    else{n = 3*n+1}
  }
  print("success!")
}

try(fun(-1),silent = T)
fun(13)
fun_1(13)