2019 R Bridge Week 1 Assignment

1. Write a loop that calculates 12-factorial

result <- 1
num <- 1:12
calc_factorial <- function()
{
    for(i in num){
        result <- result*num[i]
    }
    print(result)
}

calc_factorial()

## [1] 479001600

2. Show how to create a numeric vector that contains the sequence from 20 to 50 by 5.

create_vect <- function(){
    vec <- seq(from=20, to=50, by=5)
    print(vec)
}

create_vect()

## [1] 20 25 30 35 40 45 50

3. Create the function “factorial” that takes a trio of input numbers a, b, and c and solve the quadratic equation. The function should print as output the two solutions

# calculate discriminant
get_dicr <- function(a,b,c){
      b**2-4*a*c
}

#evaluate the quadratic function
factorial <- function(a,b,c){
  if(get_dicr(a,b,c) > 0){ # first case D>0
    root_1 = (-b+sqrt(get_dicr(a,b,c)))/(2*a)
    root_2 = (-b-sqrt(get_dicr(a,b,c)))/(2*a)
    paste0("The roots of the equation are: ", root_1, " and ", root_2)
    
  }else if(get_dicr(a,b,c) == 0){
        root <- -b/(2*a)
        paste0("The given numbers produced a single root: ", root)
  }
  else {
    print("The given numbers do not produce real roots.")}
}

#test for three scenarios: single root, two roots, no real roots
factorial(1,2,1) 

## [1] "The given numbers produced a single root: -1"

factorial(3,-4,1)

## [1] "The roots of the equation are: 1 and 0.333333333333333"

factorial(4,-1,3)

## [1] "The given numbers do not produce real roots."