Functions

f <- function() {
  # this is an empty function with no arguments or body code
}

class(f)

## [1] "function"

f()

## NULL

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

## [1] "Hello, world!"

cat is to catonate

f <- function(friend){
      cat("Hello", friend, "!\n")
}

f("Mike")

## Hello Mike !

f(50)

## Hello 50 !

Add some intelligence and error capturing

f <- function(friend){
        if(is.character(friend)) {
          cat(paste0("Hello ", friend, "!\n"))
        }
          else {
            warning("You didnt not enter a character string!")
          }
}
f("Mike")

## Hello Mike!

f(50)

## Warning in f(50): You didnt not enter a character string!

Default argument

f <- function(friend = "my friend"){
        if(is.character(friend)) {
          cat(paste0("Hello ", friend, "!\n"))
        }
          else {
            stop("You didnt not enter a character string!")
          }
}
f()

## Hello my friend!

f("Mike")

## Hello Mike!

Fahrenheit/Celsius Conversion

convertTemp <- function(degrees, type = "F"){v
  `%!in` <- Negate(`%in%`)
  if(type %!in% c("F", "C", "f", "c")){
    
    warning('Enter "C" for Celsius or "F" (or blank for Fahrenheit)')
  }
  if(type == "F" | type == "f"){
    result <- round((degrees - 32) * (5/9), 1)
    cat(paste0(degrees,
                " Fahrenheit is ", result, "Celsius\n"))
        #return(result)
        
    
  } else if ( type == "C" | type == "c") {
    result <- round((degrees * 9/5)+ 32, 1)
    cat(paste0(degrees,
               " Celcius is ", result, " Farhrenheit=\n"))
  }
}

find_mode <- function(x){
  u <- unique(x)
  tab <- tabulate(match(x, u))
  u[tab == max(tab)]
}

find_mode(c(0,0,0,1,1,1,4,4,7,10))

## [1] 0 1

#anonymous function

f <- function(friend){
      cat("hello", friend, "!\n")
}
f("Mike")

## hello Mike !

rewrite

(function (x) {cat("Hello", x, "!\n")}) ("Mike")

## Hello Mike !

BMI IN R

BMI = WEIGHT / HEIGHT^2 x 703

weight <- readline(prompt = "Enter Your Weight(in pounds): ")

## Enter Your Weight(in pounds):

height <- readline(prompt = "Enter Your Height(in inches): ")

## Enter Your Height(in inches):

#convert to numeric
weight <- as.numeric(weight)
height <- as.numeric(height)

bmi <- weight / (height*height) *703

print(paste("Your BMI is:", bmi))

## [1] "Your BMI is: NA"