Color Planes

In Figure 2, we have added a color bar to Figure 1. Again, each point on the top line represents the plant's growth rate as a function of inches of water per week with 14 hours of sunlight per day; the next line with 11 hours per day, etc.  Now what if we added another independent variable: fertilizer? Let's assume the experiment was repeated. This time six groups of plants were grown with a different amount of fertilizer added to each group. The growth data for each group would produce a graph similar to Figure 2 as shown in Figure 3.

Figure 2-Color bar indicated plant growth equals a color.


Figure 3- Six graphs, showing the different plant growth as a result of varying rates in fertilizer application.

Normally, a second independent variable is added on the z-axis creating a 3D Graph. However, if we put the six 2D graphs in Figure 3 together in one 3D graph, it would be a really confusing graph! So let's look at another way to VISUALIZE this data.

In Figure 4, the higher the point is on the y-axis, the greater the growth rate. If a color bar is placed along the y-axis, so that the maximum value of plant growth is equal to red, and the minimum value is equal to purple, then each point of the line can be presented by a color.

Figure 4- Each point of the top graph is equal to a color.

The point at the top of the curve is colored red, since red stands for a maximum value. The point no longer needs to be on a curve for the viewer to know that it is a maximum value. The color takes the place of the y-axis, because the color represents growth rate just as the y-axis did. The curve can then be compressed into a single horizontal line of color. Red represents where the curve used to be at a maximum, and the purple represents where the curve used to be a minimum.

Figure 5- The color line below the graph represents the plant growth at 14 hours of sun per day.

Similarly, color can be substituted for each point on the other four graphs. The five lines of color are then stacked on top of each other in a square. The colors represent plant growth, the x-axis is still the amount of rain per week, but the y-axis is now the amount of sunlight per day.

Figure 6- The color represents plant growth, with the amount of water on the x-axis and amount of sun on the y-axis.

This movie illustrates the process of creating a color plane.

Click on the icon to download movie (1.66 mb)

This movie requires Windows Media Player 


Constructed solely for this tutorial, the above figures do not represent valid agricultural data.

Copyright © 1998 Central Virginia Governor's School for Science and Technology Lynchburg, VA