19 R判断控制函数练习

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> x=rnorm(1,3,1) > if(x>3) y=1 else y=0 > y [1] 1 > ifelse(rbinom(10,1,0.5),"字","花") [1] "花" "字" "花" "字" "花" "字" "字" "花" "字" "花" > set.seed(1) > x=c("A","B","C","A","D") > ifelse(x=="C","否",ifelse(x=="D",NA,"是"))#只能替换 [1] "是" "是" "否" "是" NA > for (i in x) {#遍历替换x里的元素 + j=match(i,x)#返回下标位置 + x1=switch(i,"A"="是","B"="是","C"="否","D"="NA") + x[j]=x1 + + } > x [1] "是" "是" "否" "是" "NA" > for (i in letters[1:5]) { + print(i) + } [1] "a" [1] "b" [1] "c" [1] "d" [1] "e" > m=matrix(1:6,2,3) > m [,1] [,2] [,3] [1,] 1 3 5 [2,] 2 4 6 > for(i in 1:2){ + for(j in 1:3){ + print(m[i,j]) + } + } [1] 1 [1] 3 [1] 5 [1] 2 [1] 4 [1] 6 > j=1 > count=0 > while(count<6){ + print(count) + count=count+1 + } [1] 0 [1] 1 [1] 2 [1] 3 [1] 4 [1] 5 > x=5 > while(x>=3 &x<10){ + print(x) + x=ifelse(rbinom(10,1,0.5),x+1,x+0) + + } [1] 5 [1] 5 5 6 6 5 6 6 6 6 5 [1] 5 5 7 6 6 6 7 7 6 6 [1] 6 5 8 6 6 6 7 7 7 6 [1] 6 6 8 6 7 7 8 7 8 6 [1] 7 7 9 7 8 8 8 7 9 7 [1] 7 8 9 7 8 8 8 8 10 7 [1] 8 8 9 7 9 8 8 9 10 8 [1] 8 9 9 7 9 9 9 9 11 9 [1] 8 10 9 7 10 9 10 9 11 9 [1] 8 10 10 8 11 10 10 9 12 10 [1] 9 10 10 9 12 10 10 9 13 11 There were 12 warnings (use warnings() to see them) > for (i in 1:20) { + if(i<10) next + print(i) + } [1] 10 [1] 11 [1] 12 [1] 13 [1] 14 [1] 15 [1] 16 [1] 17 [1] 18 [1] 19 [1] 20 > loan=c("A","B","D","C","C","B","A","B","A","D") > ifelse(loan=="D","否",ifelse(loan=="B","NA","是"))#向量判断替换 [1] "是" "NA" "否" "是" "是" "NA" "是" "NA" "是" "否" > m=matrix(1:81,9,9) > for (i in 1:9) { + x=1:9 + m[i,]=x*i + } > m [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [1,] 1 2 3 4 5 6 7 8 9 [2,] 2 4 6 8 10 12 14 16 18 [3,] 3 6 9 12 15 18 21 24 27 [4,] 4 8 12 16 20 24 28 32 36 [5,] 5 10 15 20 25 30 35 40 45 [6,] 6 12 18 24 30 36 42 48 54 [7,] 7 14 21 28 35 42 49 56 63 [8,] 8 16 24 32 40 48 56 64 72 [9,] 9 18 27 36 45 54 63 72 81 > x=as.matrix(1:9) > y=t(as.matrix(1:9)) > m=x%*%y > m [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [1,] 1 2 3 4 5 6 7 8 9 [2,] 2 4 6 8 10 12 14 16 18 [3,] 3 6 9 12 15 18 21 24 27 [4,] 4 8 12 16 20 24 28 32 36 [5,] 5 10 15 20 25 30 35 40 45 [6,] 6 12 18 24 30 36 42 48 54 [7,] 7 14 21 28 35 42 49 56 63 [8,] 8 16 24 32 40 48 56 64 72 [9,] 9 18 27 36 45 54 63 72 81 > 1:9 %*%t(1:9) #强制转换成了1：9的矩阵，矩阵相乘用%*% [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [1,] 1 2 3 4 5 6 7 8 9 [2,] 2 4 6 8 10 12 14 16 18 [3,] 3 6 9 12 15 18 21 24 27 [4,] 4 8 12 16 20 24 28 32 36 [5,] 5 10 15 20 25 30 35 40 45 [6,] 6 12 18 24 30 36 42 48 54 [7,] 7 14 21 28 35 42 49 56 63 [8,] 8 16 24 32 40 48 56 64 72 [9,] 9 18 27 36 45 54 63 72 81 > ?print > for (i in 1:9) {#print实现不换行，还没找到方法，用cat可以实现 print竖线打印，cat横线打印 + for (j in 1:i) { + x=i*j + #a=paste(c(i,"*",j,"=",x," "),collapse="") + cat(i,"*",j,"=",x," ") + } + cat("\n") + } 1 * 1 = 1 2 * 1 = 2 2 * 2 = 4 3 * 1 = 3 3 * 2 = 6 3 * 3 = 9 4 * 1 = 4 4 * 2 = 8 4 * 3 = 12 4 * 4 = 16 5 * 1 = 5 5 * 2 = 10 5 * 3 = 15 5 * 4 = 20 5 * 5 = 25 6 * 1 = 6 6 * 2 = 12 6 * 3 = 18 6 * 4 = 24 6 * 5 = 30 6 * 6 = 36 7 * 1 = 7 7 * 2 = 14 7 * 3 = 21 7 * 4 = 28 7 * 5 = 35 7 * 6 = 42 7 * 7 = 49 8 * 1 = 8 8 * 2 = 16 8 * 3 = 24 8 * 4 = 32 8 * 5 = 40 8 * 6 = 48 8 * 7 = 56 8 * 8 = 64 9 * 1 = 9 9 * 2 = 18 9 * 3 = 27 9 * 4 = 36 9 * 5 = 45 9 * 6 = 54 9 * 7 = 63 9 * 8 = 72 9 * 9 = 81