In class activities

student.df <- data.frame(name = c("Sue","Eva","Henry", "Jan"),
                         sex = c("f","f","m","m"),
                         years = c(21,31,29,19))

student.df$male.teen <- ifelse(student.df$sex == "m" & student.df$years > 20, "T", "F")

student.df <- data.frame(name = c("Sue","Eva","Henry", "Jan"),sex = c("f","f","m","m"),years = c(21,31,29,19),male.teen = ifelse(student.df$sex == "m" & student.df$years < 20, "T","F"))

student.df

##    name sex years male.teen
## 1   Sue   f    21         F
## 2   Eva   f    31         F
## 3 Henry   m    29         F
## 4   Jan   m    19         T

set.seed(4)
r <- rnorm(3)
reps <- 1
repeat {
  print(r)
  reps <- reps+1
  if (reps>10){
    break
  }
}

## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446
## [1]  0.2167549 -0.5424926  0.8911446

for (i in mtcars$disp){
  if (i < 160)
    next
  print(i)
}

## [1] 160
## [1] 160
## [1] 258
## [1] 360
## [1] 225
## [1] 360
## [1] 167.6
## [1] 167.6
## [1] 275.8
## [1] 275.8
## [1] 275.8
## [1] 472
## [1] 460
## [1] 440
## [1] 318
## [1] 304
## [1] 350
## [1] 400
## [1] 351
## [1] 301

for (i in mtcars$disp){
  if (i > 160)
    break
  print(i)
}

## [1] 160
## [1] 160
## [1] 108

y <- c(3,9,13,19,23,29)
 

x <- c(1:30)
x = x[!(x %in% y)]
print(x)

##  [1]  1  2  4  5  6  7  8 10 11 12 14 15 16 17 18 20 21 22 24 25 26 27 28 30

a <- c(3, 7, NA, 9)
b <- c(2, NA, 9, 3)
f <- c(5, 2, 5, 6)
d <- c(NA, 3, 4, NA)
mydf <- data.frame(a = a, b = b, f = f, d = d)

mydf$e <- ifelse(is.na(mydf$a), mydf$b, 
                 ifelse(is.na(mydf$b), mydf$d, mydf$f))


print(mydf)

##    a  b f  d e
## 1  3  2 5 NA 5
## 2  7 NA 2  3 3
## 3 NA  9 5  4 9
## 4  9  3 6 NA 6

n <- 5

mat <- matrix(NA_integer_, nrow = n, ncol = n)

for (i in 1:n) {
  for (j in 1:n) {
    mat[i, j] <- abs(i - j)
  }
}

diag(mat) <- 0

print(mat)

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