Lab9x - Programming in R - Control Structures and Functions

Generate a uniform random number

x <- runif(1, 0, 10)  
if(x >= 5) {
        y <- 10
} else {
        y <- 0
}
print(paste("x =",x))

## [1] "x = 1.47554446943104"

print(paste("y =",y))

## [1] "y = 0"

for Loops

for(i in 1:10) {
  x <- runif(1, 0, 10)  
       if(x >= 5) {
        y <- 10
} else {
        y <- 0
}
print(paste("x =",x))
print(paste("y =",y))
}

## [1] "x = 2.92206051992252"
## [1] "y = 0"
## [1] "x = 0.949345475528389"
## [1] "y = 0"
## [1] "x = 8.56714182300493"
## [1] "y = 10"
## [1] "x = 7.47034611646086"
## [1] "y = 10"
## [1] "x = 7.7326493174769"
## [1] "y = 10"
## [1] "x = 9.01053166249767"
## [1] "y = 10"
## [1] "x = 2.48504071030766"
## [1] "y = 0"
## [1] "x = 6.92257595947012"
## [1] "y = 10"
## [1] "x = 7.74420728441328"
## [1] "y = 10"
## [1] "x = 5.81402687821537"
## [1] "y = 10"

Generate a sequence based on length of ‘x’

x <- runif(10, 0, 100)
for(i in seq_along(x)) {   
        print(x[i])
}

## [1] 86.40791
## [1] 83.42881
## [1] 82.90428
## [1] 2.773488
## [1] 23.80169
## [1] 61.26571
## [1] 91.02837
## [1] 2.8072
## [1] 59.31704
## [1] 36.99571

for(letter in x) {
        print(letter)
}

## [1] 86.40791
## [1] 83.42881
## [1] 82.90428
## [1] 2.773488
## [1] 23.80169
## [1] 61.26571
## [1] 91.02837
## [1] 2.8072
## [1] 59.31704
## [1] 36.99571

for(i in 1:4) print(x[i])

## [1] 86.40791
## [1] 83.42881
## [1] 82.90428
## [1] 2.773488

Nested For Loops

x <- matrix(1:6, 2, 3)
for(i in seq_len(nrow(x))) {
        for(j in seq_len(ncol(x))) {
                print(x[i, j])
        }   
}

## [1] 1
## [1] 3
## [1] 5
## [1] 2
## [1] 4
## [1] 6

While Loops

count <- 10
while(count < 100) {
        print(count)
        count <- count * 2
}

## [1] 10
## [1] 20
## [1] 40
## [1] 80

z <- 5
set.seed(1)
while(z >= 3 && z <= 10) {
        coin <- rbinom(1, 1, 0.5)
        
        if(coin == 1) {  ## random walk
                z <- z + 1
        } else {
                z <- z - 1
        } 
}
print(z)

## [1] 2

Functions

f <- function() {
        cat("Hello, world!")
}
f()

## Hello, world!

f <- function(num) {
        for(i in seq_len(num)) {
                cat("Hello, world!")
        }
}
f(10)

## Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!

f <- function(num) {
        hello <- "Hello, world!\n"
        bye <- "Bye, world!\n"
        for(i in seq_len(num)) {
                cat(hello,bye)
        }
        chars <- (nchar(hello) + nchar(bye)) * num
        chars
}
meaningoflife <- f(3)

## Hello, world!
##  Bye, world!
## Hello, world!
##  Bye, world!
## Hello, world!
##  Bye, world!

print(meaningoflife)

## [1] 78