Simple Exercises with Solutions

Topics: exercises
Exercise 1: BMI Calculator Script

Goal:

Write a simple script (bmi_calculator.R) that computes Body Mass Index (BMI) and interprets the result.

Instructions:

  1. Create a function calculate_bmi(weight, height) that:
    • Takes weight (in kilograms) and height (in meters)
    • Returns the BMI value
  2. Create another function interpret_bmi(bmi) that:
    • Returns “Underweight”, “Normal weight”, “Overweight”, or “Obese” depending on the BMI
  3. In the main script (main.R), ask the user for their weight and height, then print their BMI and category.

bmi_calculator.R

# Simple BMI Calculator Script

calculate_bmi <- function(weight, height) {
  # Compute BMI = weight / height^2
  weight / (height ^ 2)
}

interpret_bmi <- function(bmi) {
  # Return BMI classification.
  if (bmi < 18.5) {
    return("Underweight")
  } else if (bmi < 25) {
    return("Normal weight")
  } else if (bmi < 30) {
    return("Overweight")
  } else {
    return("Obese")
  }
}

main.R

source("bmi_calculator.R")

weight <- as.numeric(readline(prompt = "Enter your weight (kg): "))
height <- as.numeric(readline(prompt = "Enter your height (m): "))

bmi_value <- calculate_bmi(weight, height)
category  <- interpret_bmi(bmi_value)

cat(sprintf("Your BMI is %.1f (%s)\n", bmi_value, category))
Exercise 2: Medication Dosage Calculator

Goal:

Create a function that calculates a child’s drug dosage based on weight (e.g., for Paracetamol).

Instructions:

  1. The safe dose for Paracetamol is 10–15 mg/kg per dose.
  2. Create a script (dosage_calculator.R) with:
    • Function calculate_dosage(weight, dose_mg_per_kg)
    • Function recommend_range(weight) that prints the safe dosage range (10–15 mg/kg)
  3. Test with a few sample inputs.

dosage_calculator.R

# Simple medication dosage calculator

calculate_dosage <- function(weight, dose_mg_per_kg) {
  # Calculate dose in mg given weight in kg.
  weight * dose_mg_per_kg
}

recommend_range <- function(weight) {
  # Print recommended Paracetamol dose range (mg).
  min_dose <- calculate_dosage(weight, 10)
  max_dose <- calculate_dosage(weight, 15)
  cat(sprintf("Safe range: %.0f mg - %.0f mg per dose\n", min_dose, max_dose))
}

main.R

source("dosage_calculator.R")

weight <- as.numeric(readline(prompt = "Enter child's weight (kg): "))
recommend_range(weight)

chosen_dose <- as.numeric(readline(prompt = "Enter dose in mg/kg (10-15): "))
total_mg    <- calculate_dosage(weight, chosen_dose)

cat(sprintf("Total dose: %.0f mg\n", total_mg))
Exercise 3: Heart Rate Evaluator

Goal:

Create a function that classifies a resting heart rate reading based on simple rules.

Instructions:

  1. Create a script (heart_rate.R) with:
  2. Function classify_heart_rate(rate)
  3. Classification rules:
    • Below 60 → “Bradycardia”
    • 60–100 → “Normal”
    • Above 100 → “Tachycardia”
  4. Test the function using different values.

heart_rate.R

# Heart rate classification script

classify_heart_rate <- function(rate) {
  # Return classification of resting heart rate.
  if (rate < 60) {
    return("Bradycardia (Low heart rate)")
  } else if (rate <= 100) {
    return("Normal")
  } else {
    return("Tachycardia (High heart rate)")
  }
}

main.R

source("heart_rate.R")

rate           <- as.integer(readline(prompt = "Enter resting heart rate (bpm): "))
classification <- classify_heart_rate(rate)

cat(sprintf("Heart Rate: %d bpm → %s\n", rate, classification))
Errors and Exception Handling Summary