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1 Pie Charts


									1    Raw Data is Ugly
Graphical representations of data always look pretty in newspapers, magazines
and books. What you haven’ seen is the blood, sweat and tears that it some-
times takes to get those results. But you will!




    The previous examples are informative graphical displays of data. They all
started life as bland data sets.

2      Pie Charts
Pie charts are a visual method for displaying the categories of a collection of
data. The size of a slice of the pie chart is proportional to the percentage of
data in that category.

Example 1 Consider the distribution of hits over the career of Babe Ruth. We
visually represent this data in a pie chart. We can label the slices with either
the raw numbers of percentages for each category

Babe Ruth   At Bats
Single          1517
Double           506
Triple           136
HR               714
Out             5526

 Babe Ruth

            Pie chart with raw numbers

    Pie chart with percentages and wedge

Example 2 Here we display the number of games played, broken down by team,
for Michael Jordan and Nolan Ryan.

Michael Jordan   Games Played
Bulls                      930
Wizards                    142

Nolan Ryan       Games Played
Mets                       105
Angels                     291
Astros                     282
Rangers                    129

 Games played by Team

    Pie chart of Michael Jordan
          basketball teams

 Pie chart of Nolan Ryan baseball

Example 3 You must be careful not to overload a pie chart with too much
detail. The distribution of tiles at the start of a game of Scrabble is given below.
This seems like a natural concept to represent with a pie chart. However, once
you construct the pie chart for this distribution it is easy to see that too much
information is contained in the picture.
  Letter Frequency Letter Frequency Letter Frequency
  a       9            j         1              s       4
  b       2            k         1              t       6
  c       2            l         4              u       4
  d       4            m         2              v       2
  e       12           n         6              w       2
  f       2            o         8              x       1
  g       3            p         2              y       2
  h       2            q         1              z       1
  i       9            r         6              blank   2

       Frequencies of Scrabble tiles

3     Importing Data into Excel 2007
It is easy to use Excel 2007 to grab tables of data o¤ the web. Let’ say we wish
to import the table of Passing statistics of Joe Namath from the pro-football- website.

     Joe Namath page at

In an Excel 2007 spreadsheet, select the location where you wish to place the
table of data. Select the Data tab. Select From Web.

Preparing to import data into Excel

A new window will pop up. Type in the address of web page that contains the
desired data. You can use this window to surf until you …nd your destination.
Click the yellow arrow beside the desired table.

          Locating data on the web

Click Import. Click Ok. Now you have the table of data in an Excel spread-
sheet, ready for use.

                     Ready to use

4    Turning Data into Pie Charts
This table includes a lot of statistics and we may only be concerned with certain
variables. Let’ keep only the variables for Year, Games Played (G), Passes
Completed (Cmp), Passes Attempted (Att), Yards (Yds), Touchdowns (TD)
and Interceptions (Int). Rather than delete the individual pieces of data, we
wish to delete the whole column. To remove the column B which contains Age
data, right click B and select delete. You will see that this technique shifts all
the data to the left so we are not left with empty columns. Repeat until we
have only the desired variables remaining.

 After the removal
 of unwanted data

Let’ construct a pie chart for the number of games Namath played per season.
Highlight the years and games played column. Click Insert. Click Pie.

       Making a pie chart

Excel now asks for a style of pie chart. Let’ keep it simple and select the …rst
option from the 2-D category.

                The initial picture

Right now we have a colorful but highly uninformative picture. Let’ add    s
labels to our pie slices. With the pie chart selected, click Layout. Click Data
Labels. Click Best Fit. This will label each wedge its representative label.
Click on the title and expand its description.

                  Adding info

Excel provides lots of opportunities for customizing. We might wish to label
the wedges with the percentage of the pie it occupies and or include the category
name. Right click on any wedge in the pie and select Format Data Labels.
Check the boxes for Category Name and Percentage. Our pie chart now
has more information. Of course, we may run the risk of a visual that is too
crowded to be attractive. Stylistic choices of the pie chart fall into the category
of art rather than science.

                   A …nished product

    Next let’ create a 3-D chart of touchdowns over the years for Joe Namath.
The touchdown column is not beside the years column. It is not di¢ cult to
select just those two columns. Highlight the years column. Hold the Ctrl key
while highlighting the TD column. Release the Ctrl key and we have selected
the two desired columns. Select the 3-D pie. Format the labels with just the
legend and percentages.

                     A …nished 3-D pie graph

    Joe Namath played for one team in every season of his career. He never
changed teams mid-season. Due to this, his career statistics are very easy to
read and well organized. Namath played in a di¤erent era of sports. Players
today frequently change teams in the middle of a season. Consider the career
stats of Cli¤ Lee as of May 3, 2011. If we want to created a games played per
season pic chart for Cli¤ Lee, we cannot simply import the data into Excel and
create the pie chart. If we did so, we would have three pie wedges each for 2009
and 2010. We need to modify the data for our chart.

5     Exercises
    1. Based on the following pie chart, which KSU student spent the most years
       playing professional major league baseball?

                       KSU Owls in MLB

    2. Import data from and construct a pie chart for
       the number of games played broken down by team for hockey great Wayne
    3. Import data from and construct a pie chart
       for the number of games played broken down by team for the shortest man
       to play in the NBA, Tyrone "Muggsy" Bogues.
    4. In week one of the 2010 NFL season, The Houston Texans beat the Indi-
       anapolis Colts 34 to 24. Rushing and receiving stats for the game appear
       Rushing         Attempts        Yards         TD       Lg
       Arian Foster               33           231        3        42
       Steve Slaton                6            29        0        13
       Matt Schaub                 3            -3        0        -1

       Receiving       Attempts        Yards         TD       Lg
       Andre Johnson              3            33         0        21
       Jacoby Jones               2            29         0        23
       Kevin Walter               2            29         1        22
       Owen Daniels               1             9         0         9
       Arian Foster               1             7         0         7
      i. Construct a pie chart for yards passing for the …ve Texan receivers.
      ii. What di¢ culty should you encounter if you attempt to construct a pie
      chart for yards rushing? What does Excel do?
    5. Go to and construct a pie chart
       of the frequencies of 5 card poker hands.

6. Up to and including the year 2010 create a pie chart by team for the num-
   ber of championships won in the ABA. Visit¤s/
   for the data.
7. Up to and including the year 2010 create a pie chart by team for the num-
   ber of championships won in the NBA. Visit¤s/
   for the data.
8. Some statistics on Baseball Hall of Fame pitcher Steve Carlton are given
   Steve Carlton
   Uniform Number           32
   Rookie Year            1965
   Number of Teams           6
   Career Wins             329
   Cy Young Awards           4
   Complete Games          254
  Does it make sense to use a pie chart to represent this data?

          Quantitative data about Steve Carlton


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