R-Studio Notebook Control Structures.Rmd

---
title: 'R Notebook: Lesson 3, Control Structures'
output:
  html_document:
    df_print: paged
---

An If Statement and a For Loop

```{r}
# take input from the user 

num <- as.integer(readline(prompt="Enter a number: ")) 

factorial <- 1 

# check is the number is negative, positive or zero 
if(num < 0) { 

   print("Sorry, factorial does not exist for negative numbers") 

} else if(num == 0) { 

   print("The factorial of 0 is 1") 

} else { 

   for(i in 1:num) { 

      factorial = factorial * i 
   } 
   print(paste("The factorial of", num ,"is",factorial)) 
} 

```

The ifelse() command
A shorthand function, typically used with vectors

```{r}

# define a vector of numbers
A = c(5, 7, 2, 22, 31, 9)
B <- ifelse(A %% 2 == 0,"even","odd")
#B
```

A While Loop

```{r}
# checking for an Armstrong number
#
# an Armstrong or Narcissistic number is a number 
# whose value is equal to the sum of the cubes of 
# its own digits
# e.g. 370 = 3*3*3 + 7*7*7 + 0*0*0
#      370 = 27 + 343 + 0 

num = as.integer(readline(prompt="Enter a number: ")) 

sum <- 0 
temp = num 

while(temp > 0) { 

   digit = temp %% 10 
   sum = sum + (digit ^ 3) 
   temp = floor(temp / 10) 

} 

if(num == sum) { 

   print(paste(num, "is an Armstrong number")) 

}

```

Dress Shopping with 'next' and 'break'.

```{r}
dresses <- c("Prada", "CK", "YSL", "Gucci", "Guess")

for(d in dresses) {
  
  print(d)

  if (d == "CK") {
    print("I don’t like CK! Please bring me the next one.")
	  next
  }
  
  if (d == "Gucci") {
    print("Squee! I found it!")
    break
  }

}

```

Lesser Used: The repeat loop

```{r}
x <- 10
repeat {
  print(paste(x, " bottles of beer on the wall, ", x, " bottles of beer!"))

  if (x == 1){
    print("Saving the last one for later!")
    break
  } else {
    print("Take one down and pass it around...")
  }
  x = x-1
}
```