Graphs and charts provide lots of information quickly. It’s true that a picture is worth a thousand words. After all, you can quickly grasp the financial situation of a business when you see a line on a graph that represents earnings sloping down.
The more common types of graphs are scattered plots, line graphs, and bar graphs (or histograms). Scatter plots are numbers represented by dots distributed about a rectangular area. A line graph connects points to one another. Trends and items that are connected — that affect one another — are best shown with line graphs. In the section on line graphs, you see how to get around the need for uniform labeling. You also see how graphs can be abused.
Organizing Scattered Information with a Scatter Plot
A scatter plot may look just like what its name implies: a bunch of dots scattered all over the place. A scatter plot is used to see whether the data that it represents has any visible trend or pattern. If the dots are scattered all over the chart with no rhyme or reason, you can safely conclude that there’s no correlation between the values that are being plotted. However, if you see the plotted dots lying more in a clump or in an upward-leaning gathering, you may determine that some connection or trend is taking place between the values.
Lining Up Data with Line Graphs
A line graph actually consists of a bunch of connected segments. A line graph connects data that occurs sequentially over a period of time. You use a line graph to show how values are connected when one point affects the next one. For example, a line graph often is used to show how temperatures change during a day because the temperature one hour affects the temperature the next hour. Another use for a line graph is to show the depreciation of a piece of machinery or other property. The value of an item one year has a bearing on the item’s value the next year. The following sections explain everything you need to know about line graphs
Creating a line graph
The axes used when creating a line graph have numbers or values representing different aspects of the data. The two axes usually have different numbering systems, because the values being compared most likely don’t even have the same units. But the numbering on each axis should be uniform — spaced equally and numbered consecutively.
Indicating gaps in graph values
You want your graphs and charts to do a lot of explaining without words. So you need to label the axes carefully, use a uniform scale on the axes, and plot the values carefully.
Some data sets don’t cooperate very well when it comes to setting up axes that are constructed correctly and, at the same time, give good information. Sometimes, for instance, problems arise when you want the intersection of the axes to be 0 and the numbers to increase as you move to the right and upward. But you don’t want your graph to be, say, 6 inches across and 90 inches high just to accommodate the numbering protocol. Instead, in this case, you should indicate a gap in the numbering with a zigzag on the axis.
A pie chart is a circle divided into wedges where each wedge or piece of the pie is a proportionate amount of the total — based on the actual numerical figures. Pie charts are especially useful for showing budget items — where certain amounts of money are going. To create a pie chart, you divide the circle proportionately and draw in the radii (the edges of the pieces). The following sections explain pie charts in more detail.