Lab 4

1. Write R scripts using the selection flow control for each of the following.

1. Determine the biggest number among three numbers.

num_list<-list()
num_list[1]<-as.integer(readline("Enter a number:"))
13
num_list[2]<-as.integer(readline("Enter a number:"))
2
num_list[3]<-as.integer(readline("Enter a number:"))
5
max_num <- num_list[1]
for (num in num_list){
  if (num > max_num){
    max_num<-num
  }
}
print(max_num)

[[1]]
[1] 13

2. A switch statement that displays Sunday, Monday, …, Saturday, if the number is 0, 1, … 6.

num<-readline("Enter a number: ")
11
switch(num,
       "0"="Monday",
       "1"="Tuesday",
       "2"="Wednesday",
       "3"="Thursday",
       "4"="Friday",
       "5"="Saturday",
       "6"="Sunday",
       "Out of Bounds")

[1] "Out of Bounds"

3. Determine whether the year is a leap year. A leap year is divisible by 4 but not by 100. A leap year is also divisible by 400.

isLeapYear<-function(year){
  if (year%%400==0 | (year%%4==0 & year%%100!=0)){
    return(TRUE)
  }
  return(FALSE)
}
year<-as.integer(readline("Enter a year: "))
1904
isLeapYear(year)

[1] TRUE

2. Write R scripts using the ifelse() function for each of the following.

1. Determine the positive and negative number in the vector.

nums <- sample(-10:10,5)
nums

[1] -4  0 10  1  4

for (num in nums){
  print(ifelse(num<0,"Negative","Positive"))
}

[1] "Negative"
[1] "Positive"
[1] "Positive"
[1] "Positive"
[1] "Positive"

2. Determine whether a character in the vector is uppercase or lowercase letter.

letters=c("A","a","b","B")
for (letter in letters){
  print(ifelse(letter==toupper(letter),"Uppercase","Lowercase"))
}

[1] "Uppercase"
[1] "Lowercase"
[1] "Lowercase"
[1] "Uppercase"

3. Compare the numbers from two vectors to determine whether a number is larger than, smaller than or equal to another number.

v1<-sample(1:10,2)
v2<-sample(1:10,2)
for (n1 in v1){
  for (n2 in v2){
    if (n1<n2){
      print(paste(n1," is smaller than ",n2))
    }else if (n1>n2){
      print(paste(n1," is greater than ",n2))
    }else{
      print(paste(n1," is equal to ",n2))
    }
  }
}

[1] "10  is equal to  10"
[1] "10  is greater than  4"
[1] "8  is smaller than  10"
[1] "8  is greater than  4"

3. Create an R file named calculator.r that stimulates a simple calculator. It reads two numbers and an operator. If the operator is +, the sum is printed; if it is -, the difference is printed; if it is x, the multiplication is printed; if it is /, the quotient is printed.

nums<-readline("Enter two numbers: ")
11 14
nums<-strsplit(nums," ")
n1<-as.numeric(nums[[1]][1])
n2<-as.numeric(nums[[1]][2])
op<-readline("Enter operator: ")
*
switch(op,
       "+"=print(paste(n1,op,n2,"=",n1+n2)),
       "-"=print(paste(n1,op,n2,"=",n1-n2)),
       "*"=print(paste(n1,op,n2,"=",n1*n2)),
       "/"=print(paste(n1,op,n2,"=",n1/n2)),
       "Unsupported operator")

[1] "11 * 14 = 154"

4. Create an R file named circle.r. The script will ask user to enter the radius of a circle and a coordinate point (x, y). Determine whether the point is inside or outside the circle centered at (0, 0).

calcDist<-function(x,y){
  return(sqrt(x**2+y**2))
}
r=readline("Enter the radius of the circle: ")
5
c=readline("Enter the coordinate x and y: ")
3 4
x=as.integer(strsplit(c," ")[[1]][1])
y=as.integer(strsplit(c," ")[[1]][2])
print(ifelse(calcDist(x,y)<=r,paste("(",x,",",y,") is in the circle"),paste("(",x,",",y,") is not in the circle")))

[1] "( 3 , 4 ) is in the circle"

5. Write R statements using loop flow control for each of the following

1. Find the largest integer n so that n3 is less than 2000.

n<-0
while((n+1)**3<2000) {
  n<-n+1
}
print(n)

[1] 12

2. Compute the sum of the series: 1/25+2/24+3/23 … + 25/1 in two decimal places.

total=0
for (i in 1:25){
  total<-total+i/(26-i)
}
print(round(total,2))

[1] 74.21

3. Display the first ten values of the Fibonacci sequence. Given the formula f1 = 1, f2 =1, fn = fn-1 + fn-2.

fib<-function(n){
  if (n<=2){return(1)}
  return(fib(n-1)+fib(n-2))
}
for (i in 1:10){print(paste(i,":",fib(i)))}

[1] "1 : 1"
[1] "2 : 1"
[1] "3 : 2"
[1] "4 : 3"
[1] "5 : 5"
[1] "6 : 8"
[1] "7 : 13"
[1] "8 : 21"
[1] "9 : 34"
[1] "10 : 55"

6. Create an R file named score.r. The script will calculate the minimum, maximum, average and standard deviation (s) of the exam score in a subject. The program will accept the score and quit if negative score is entered.

num<-1
nums<-c()
while (num>0){
  num<-readline("Enter a score [negative score to quit]: ")
  if (num<0) break
  nums<-c(nums,as.integer(num))
}
2
3
4
-1

print(paste("Minimum score",min(nums)))

[1] "Minimum score 2"

print(paste("Maximum score",max(nums)))

[1] "Maximum score 4"

print(paste("Average score",mean(nums)))

[1] "Average score 3"

print(paste("Standard deviation",sd(nums)))

[1] "Standard deviation 1"

7. Create an R file named matrix.r. The script will ask user to enter M and N. Create a matrix with M rows and N columns with random numbers 1-50. Display the matrix and then count the number of odd and even numbers in the matrix

size<-readline("Enter M and N: ")
2 5
M<-as.integer(strsplit(size," ")[[1]][1])
N<-as.integer(strsplit(size," ")[[1]][2])
df<-matrix(sample(1:50,M*N),M,N)
odd<-0
even<-0
for (i in 1:M){
  for (j in 1:N){
    print(df[i,j])
    if (df[i,j]%%2==0) {
      even<-even+1
    } else{
      odd <-odd+1
    }
  }
}

[1] 23
[1] 2
[1] 3
[1] 4
[1] 37
[1] 27
[1] 50
[1] 28
[1] 36
[1] 31

print(paste("Number of odd numbers in the matrix:",odd))

[1] "Number of odd numbers in the matrix: 5"

print(paste("Number of even numbers in the matrix:",even))

[1] "Number of even numbers in the matrix: 5"