Classy Tuesday is here! Today's problem is to create a function that takes in a list of integers and prints out the mean, median, and mode. For a bonus also print out the standard deviation.

Comments:

• Johnathan - 10 years, 8 months ago

  Here is my python solution

  num = int(raw_input('How many integers would you like to input? '))
  
  stuff = []
  
  print 'Please enter your integers: '
  
  for i in range(num):
      x = int(raw_input('Integer: '))
      stuff.append(x)
  
  stuff.sort()
  
  
  
  def mean(list): 
      num = len(list)
      value = 0.0
  
      for i in range(num): 
          value = value + list[i]
  
      value = value/num
      return value
  
  def median(list):
      num = len(list)
      value = 0.0
  
      if num % 2 == 0:
          numx = num/2
          value = list[numx-1] + list[numx]
          value = float(value)
          value = value/2
  
      else:
          numx = num + 1
          numx = numx/2
          value = list[numx - 1]
  
      return value
  
  def mode(list):
      num = len(list)
      max = 0
      count = 0
      numbers = []
  
      for i in range(1, num):        
          if list[i] == list[i-1]:
              count = count + 1
  
              if count == max: 
                  numbers.append(list[i])
  
              elif count > max:
                  max = count
                  numbers = []
                  numbers.append(list[i])
          else:
              count = 0
      if max == 0:
          return 'There is no mode.'
      else:
          return numbers
  
  def sd(list):
      num = len(list)
      mean = 0.0
  
      for i in range(num): 
          mean = mean + list[i]
  
      mean = mean/num
  
      total = 0.0
  
      for i in range(num):
          square = list[i] - mean
          square = square * square
          total = total + square
      final = total/num
      final = final**(0.5)
      return final
  
  k = mean(stuff)
  print 'The mean is equal to',k,'.'
  
  k = median(stuff)
  print 'The median is equal to',k,'.'
  
  k = mode(stuff)
  print 'The mode is equal to',k,'.'
  
  k = sd(stuff)
  print 'The standard deviation is equal to',k,'.'
  
  t = raw_input('')
  

  reply permalink

• Max Burstein - 10 years, 8 months ago

  Nice!

  reply permalink

• David - 10 years, 8 months ago

  You can use ** for exponents.

  square**2 == square * square
  

  You can replace duplicating a variable on the operation side with [operand]= [other variable]

  value = value + list[i]
  # ^ becomes:
  value += list[i]
  

  You could also make your setup phase much more flexible by using a while loop instead of asking for the number of integers they want and asking in a for loop. As long as they give you an integer (or a float if you make a function for checking that) you ask for another.

  while(raw_input('[your_string]: ').isdigit()):  
      stuff.append(x)
  

  Although it makes your code look more consistent, you can use a for loop on the list itself rather than on a range. This makes the most sense to point out for your use in mean() and sd() where you are not referencing more than one element per iteration.

  for i in range(num):  
          value = value + list[i]
  

  becomes

  for number in list: 
          value += number
  

  Nice work

  reply permalink

• Johnathan - 10 years, 8 months ago

  Thanks for the feedback David.

  reply permalink

• Nick - 10 years, 8 months ago

  Bit late but here's my Java solution:

  import java.util.Collections;
  import java.util.List;
  
  public class MeanMedianMode {
      public static void calculateMeanMedianMode(List<Integer> input) {
          if (input == null || input.size() == 0) {
              System.out.println("Invalid input");
              return;
          }
  
          Collections.sort(input);
  
          Integer sum = 0;
  
          Integer currentRun = 0;
          Integer bestRun = 0;
          Integer mode = null;
  
          Integer lastNum = null;
  
          System.out.print("Ordered input: ");
          for (Integer elem : input) {
              System.out.print(elem + " ");
  
              sum += elem;
  
              if (elem.equals(lastNum)) {
                  currentRun++;
              }
              else {
                  if (currentRun > bestRun) {
                      mode = lastNum;
                      bestRun = currentRun;
                  }
  
                  currentRun = 1;
              }
  
              lastNum = elem;
          }
  
          if (currentRun > bestRun) {
              mode = lastNum;
          }
  
          System.out.println();
  
          Double mean = sum / Double.valueOf(input.size());
          Integer median = input.get(input.size() / 2);
  
          Double standardDeviation = calculateStandardDeviation(input, mean);
  
          System.out.println("Mean is " + mean);
          System.out.println("Median is " + median);
          System.out.println("Mode is " + mode);
          System.out.println("Standard deviation is " + standardDeviation);
      }
  
      private static Double calculateStandardDeviation(List<Integer> list, Double mean) {
          Double sumOfSquares = 0.0;
          for (Integer elem : list) {
              Double difference = elem - mean;
              sumOfSquares += (difference*difference);
          }
  
          return Math.sqrt((1D / list.size()) * sumOfSquares);
      }
  }
  

  reply permalink