Question

1. Considering a Character vector called
   statusDesc=c(“senior”,”sophomore”,”junior”,”freshman”).
   1. Write R code(s) to create a factor called statusFac that will take statusDesc as an argument and has four levels in the order of “freshman,” ”sophomore,” ”junior,” and “senior.”
      
2. Use the following codes to generate 10 random numbers to represent 10 random ages. set.seed(1)
   ages=rnorm(10,24,24)
   1. Based on the variable ages, use cut() to create a factor called ageFac that has 4 levels “child”,”teen”,”adult”, and “senior”.  

The corresponding age ranges are (3,13],(13,18],(18,60],and (60,120]. For example, one must be older than 3 and not older than 13 to be called a child. The contents of ageFac should be as follows:

[1] child adult child senior adult child adult
[8] adult adult teen
Levels: child teen adult senior

3. Assuming a variable called num contains an integer,
   1. write an if-else statement to display the message “it is an even number” if num is even, or “it is an odd number” if num is odd.
      (Hint: use %% 2 to check the remainder of num divided by 2).
      
4. Consider two variables, score and grade. The variable score contains a numeric value.
   1. Write an if-else if statement to:
      1. assign “A” to grade if score is greater than or equal to 90;
      2. assign “B” to grade if score is greater than or equal to 80 but less than 90; or
      3. assign “C” to grade if score is greater than or equal to 70 but less than 80.
         
5. Considering the following R codes
   a=c(2,-4,-3,7,6)
   b=1:5
   c=6:10
   There is a numeric vector d.
   1. Assign the item in b to d if the corresponding item in a is greater than 0,
      otherwise, assign the item in c to d.
      For instance, the first item in a is 2, which is greater than 0, therefore the first
      item of d should be 1, which comes from b. (Hint: use if-else statement).
      
6. Write a repeat loop to print out the message “Hello World!” 10 times.
   
7. Write a while loop to calculate 9! (factorial).
   
8. Considering a vector data=seq(0,100,2), which represents all the even numbers from 0 through 100,
   1. write a “for loop” to sum up all the items in data.

Answer 1

Below is the R code to execute all the above answers:

##code starts here

##character vector StatusFac
statusDesc <- c("freshman","sophomore","junior","senior");
statusFac<- as.factor(statusDesc)
statusFac

##assign 10 random numbers
set.seed(1)
ages<-rnorm(10,24,24);
ageFac <- cut(ages, breaks = c(3,13,18,60,120), labels = c("child","teen","adult","senior"));
ageFac
  
##prompt for number and check the number
## num <- as.integer(readline(prompt = "Enter number"));
num <- 5;
if(num%%2==0){
print("it is even number");
} else{
print("it is odd number");
}

##score and grade as numeric variables
score <- 95; ##you can alternatively use readline function to ask score input from the user
if(score>=90){
grade <-"A";
} else if(score >=80){
grade <- "B";
} else if(score >= 70){
grade <- "C";
}
grade

##a,b, c and, d vectors
a<-c(2,-4,-3,7,6);
b<-1:5;
c<- 6:10;
d <- vector(mode = "numeric", length = 0);
for(i in 1:5){
if(a[i]>0){
d[i]=b[i];
}
else{
d[i]=c[i];
}
}
d

##“Hello World!” 10 times

i<-1;
repeat{
print("Hello World");
if(i==10){
break;
}
i<-i+1;
}

##while loop to calculate factorial 9

i<-1;
factorial<-1;
while(i<=9){
factorial <- factorial *i;
i<-i+1;
}
factorial

##even numbers

data <- seq(0,100,2);
sumdata<-0;
for(i in data){
sumdata = sumdata +i;
}
sumdata

##code ends here

screenshot of code from RStudio