R Midpoint Rule (Rectangle Method)

Implementation of Midpoint Rule (Rectangle Method) (Integral Approximation) written in R.

Enter beginning of interval: -2
Enter end of interval: 2
Enter number of iterations: 1000000
Integral is equal to:  5.33333333334422

# ? 2018 TheFlyingKeyboard and released under MIT License
# theflyingkeyboard.net

f <- function(x) {
  return(x * x)
}	

intervalBegin <- as.double(readline(prompt = "Enter beginning of interval: "))
intervalEnd <- as.double(readline(prompt = "Enter end of interval: "))
iterations <- as.integer(readline(prompt = "Enter number of iterations: "))

step = (intervalEnd - intervalBegin) / iterations

integral = 0

for (i in 1:iterations) {
  integral = integral + step * f(intervalBegin + (i - 1) * step)
}

print(paste("Integral is equal to: ", integral))