14  CODAP Graph Basics

14.1 CODAP graphs in general

In a graph, by default, CODAP represents each case as a dot.

As we mentioned up in the commentary for the summarizing data move, CODAP is oriented to individual cases that are “atomic” bits of data, for example, people in a Census, or moments of time in a record of some phenomenon. So dots are pretty good representations.

Every graph has, basically, two axes. When you put an attribute on an axis, each dot moves so that its location corresponds to its value for that attribute.

If the attribute is numeric or a date, the axis has numbers or dates, and CODAP centers the dot on that value. If the attribute is categorical, CODAP places the dot in a bin labeled by the categorical value. By separating the dots into bins, CODAP is grouping them: categorical plots give you a data move for free.

If you plop an attribute into the middle of a graph, the points color depending on the values of that “legend” attribute. That gives you a kind of third dimension in your graph, which you can use to show additional relationships, or to emphasize one of the attributes on an axis.

People seem to understand all of that intuitively, and it gets them pretty far. But there’s more.

14.2 CODAP Graphing Tips

The next few sections describe some of the features of CODAP graphs that you might not find on your own.

14.2.1 Palettes

Blue-green palettes are attached to the right side of a graph. There is a vertical array of icons; each one has a number of controls or choices inside it.

Palettes also appear when you select a table, a map, or a slider. We’ll describe those features here as well, even though this chapter is about visualization.

The palettes appear only when the graph or table is selected. That is, there is only ever one set of palettes on the screen at a time.

icon	description
	Rescale tool. Press to show all points or rescale column widths.
	“Eyeball” palette. In a graph, use it to show or hide points. In a table, use it to set cases aside.
	“Ruler” palette. In a graph, display summaries (e.g., means, percents, standard deviation). In a table, make new attributes or export data.
	“Paintbrush” palette. Change the appearance of points in a graph. Control color, stroke, and size.
	“Snapshot” palette. Take a picture of the graph, and then export that picture. Edit the picture first if you wish in the Draw Tool.
	Configuration palette. In a graph with a numeric axis, bin the data. Where appropriate, fuse dots into bars.
	Trash can. In a table (only), delete cases.

Gotcha!

You will frequently select cases, i.e., select points in Graph A, and then want to use the eyeball tool in graph B. If you just click in Graph B, however, you may change or eliminate the selection of points! The solution is to click on Graph B’s title bar. Then the selection from Graph A is preserved.