Dot Plots

Author(s)

Prerequisites

1. Create and interpret dot plots
2. Judge whether a dot plot would be appropriate for a given data set

Dot plots can be used to display various types of information. Figure 1 uses a dot plot to display the number of M & M's of each color found in a bag of M & M's. Each dot represents a single M & M. From the figure, you can see that there were 3 blue M & M's, 19 brown M & M's, etc.

Figure 1. A dot plot showing the number of M & M's of various colors in a bag of M & M's.

The dot plot in Figure 2 shows the number of people playing various card games on the Yahoo website on a Wednesday. Unlike Figure 1, the location rather than the number of dots represents the frequency.

Figure 2. A dot plot showing the number of people playing various card games on a Wednesday.

The dot plot in Figure 3 shows the number of people playing on a Sunday and on a Wednesday. This graph makes it easy to compare the popularity of the games separately for the two days, but does not make it easy to compare the popularity of a given game on the two days.

Figure 3. A dot plot showing the number of people playing various card games on a Sunday and on a Wednesday.

Figure 4. An alternate way of showing the number of people playing various card games on a Sunday and on a Wednesday.

The dot plot in Figure 4 makes it easy to compare the days of the week for specific games while still portraying differences among games.

games = c("Poker","Blackjack","Bridge","Gin","Cribbage",
                  "Hearts","Canasta","Pinochle","Euchre","Spades")
players = c(680,1082,1635,1800,2100,2683,3189,3628,6471,7208)
dotchart(players,games)

                      

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