Example of a Contour Plot

You have data about diamonds, including their carat weight and price. Examine the relationship between carat weight and price.

1. Select Help > Sample Data Library and open Diamonds Data.jmp.

2. Select Graph > Graph Builder.

3. Select Price and drag it to the Y zone.

4. Select Carat Weight and drag it to the X zone.

Figure 4.2 Points Showing Diamond Characteristics 

You can see that the points are difficult to interpret. Some points overlap, making the density unclear.

Replace the points with a contour plot of their density.

5. Right-click the plot and select Points > Change to > Contour.

6. (Optional) Click Done.

Figure 4.3 Contour Plot of Diamond Characteristics 

The darker areas indicate a higher density of observations. Use the crosshairs tool to verify the following:

• Most people in the sample purchased diamonds with a carat weight of about 0.34 to 0.57, 0.67 to 0.75, and 0.97 to 1.05.

• Most people who purchased diamonds with a carat weight around 0.5 paid about $100-$2,000.

• Most people who purchased diamonds with a carat weight of 0.70 paid about $1,600-$2,700.

• Most people who purchased diamonds with a carat weight of 1.0 paid about $3,800-$4,800.