Activity 21

Create a new file called plotFrequency.py and save to your cs100/ch4 folder.

1. Copy and paste the following code into the file.

   import turtle
   import math
      
   #
   def mean(alist):
       mean = sum(alist) / len(alist)
       return mean
      
      
   #
   def frequencyChart(alist):
          
       #
       countdict = {}      
      
       # 
       for item in alist:
           if item in countdict:
               countdict[item] = countdict[item]+1
           else:
               countdict[item] = 1         
          
       # 
       itemlist = list(countdict.keys())
       minitem = 0
       maxitem = len(itemlist)-1
          
       #
       countlist = countdict.values()
       maxcount = max(countlist)
          
       #
       #
       wn = turtle.Screen()
       chartT = turtle.Turtle()
       wn.setworldcoordinates(-1,-1,maxitem+1,maxcount+1)
       chartT.hideturtle()
          
       #
       chartT.up()
       chartT.goto(0,0)
       chartT.down()
       chartT.goto(maxitem,0)
       chartT.up()
          
       # 
       chartT.goto(-1,0)
       chartT.write("0",font=("Helvetica",16,"bold"))
       chartT.goto(-1,maxcount)
       chartT.write(str(maxcount),font=("Helvetica",16,"bold"))
          
       #
       for index in range(len(itemlist)):
           print("Index: ", index)
           chartT.goto(index,-1)
           chartT.write(str(itemlist[index]),font=("Helvetica",16,"bold"))
              
           chartT.goto(index,0)
           chartT.down()
           chartT.goto(index,countdict[itemlist[index]])
           chartT.up()
                      
       # add code to plot mean of occurrences in red
      
       wn.exitonclick()
      
      
   #lst = [7, 11, 9, 18,15, 12]
   lst = [3,3,5,7,1,2,5,2,3,4,6,3,4,6,3,4,5,6,6]
   #lst = [2,3,4,2,3,3]
   #lst = ['a', 'b', 'c', 'd', 'f', 'c', 'b', 'c', 'a', 'd', 'a', 'b', 'b', 'c', 'b', 'a', 'c', 'd']
      
   #
   frequencyChart(lst)
   

2. Run the program with the following lists (uncomment out / comment out the assignment statements to lst in your file).

   lst = [7,11,9,18,15,12]
   lst = [17,11,28,17,11,17]
   lst = [3,3,5,7,1,2,5,2,3,4,6,3,4,6,3,4,5,6,6]
   lst = ['a', 'b', 'c', 'd', 'f', 'c', 'b', 'c', 'a', 'd', 'a', 'b', 'b', 'c', 'b', 'a', 'c', 'd']
   

3. Read and understand the code. Write short comments above each section of the program (on the lines marked by #). Use your textbook as well as the online Python resource.

4. Modify the frequency chart function to draw the mean (mean number of occurrences) as a horizontal red line.

If you finish early

Modify the frequency chart function to:

1. draw wide bars instead of lines.
2. have randomly colored bars.

How to submit

Submit your working python file plotFrequency.py to Moodle.