Creating line graphs

A line graph consists of one or more lines connecting successive attribute values. Line graphs are useful for showing how things change or move over time and what the trends in the data may be. Since a line graph uses straight line segments to connect data points, it is easy to determine the data range, minimum and maximums, gaps, clusters, and outliers.

Steps:
1. Click the View menu, point to Graphs, then click Create.
2. Click the Graph type drop-down arrow and choose the Line type—Vertical or Horizontal.

The procedure for vertical and horizontal line graphs is similar. The main difference is that, for vertical line graphs, the values from the source data field, called the Y field, are plotted on the vertical axis. For horizontal line graphs, the source data field (X field) values are plotted on the horizontal axis.

The steps below refer to a vertical line graph, but the same concepts apply to the horizontal line graph. Just replace the "Y field" references to "X field" and "X field" references to "Y field."

3. Click the Layer/Table drop-down arrow and choose the layer or table containing the data values that are to be graphed.
4. Click the Y field drop-down arrow and choose the field of values to graph. The wizard shows the initial version of the graph.
5. The points that are connected by lines are initially in the order of the data values in the source table. Change the order of the points based on another field in the optional X field parameter.

For example, you have a table with both economic (GDP) and demographic (population) fields. If you set Value field to the GDP and leave X field as the default, <None>, the points will be sorted based on the order of the values in the table.

If you then set X field to a population field and the type to Ascending, the points will be sorted with the least populous country on the left side of the graph, and as the population value increases, the points will be distributed to the right along the horizontal axis.

If nothing is explicitly set for X field, the order is the same as in the data table (record 1, record 2, and so forth).

6. Specify a different field to label the bars in the graph in X label field, commonly a text (string) field.
7. By default, the values of the input data are added to the legend of the graph. Uncheck the Add to legend check box todisable this.
8. Check the Show labels (marks) check box to mark the data points between the line sections with their actual values.

This is useful if there are adjacent points of similar value, where the small deviations in the line may not be easily seen.

9. Change the appearance of the line segments in the graph with the Color control.

The Custom setting makes all the line segments the same color. Using Palette allows you to have different colors applied to each line segment, determined from a range of predefined palettes.

10. Use Stairs mode to control how the data points are connected. When set to Off, the points will be connected directly with angled line segments.

The On and Inverted settings connect the data points with horizontal and vertical line segments. This gives a "stepped" appearance to the line graph. With the On option, the starting point of the line is the data value itself. The Inverted option changes the start point of the line to the next coordinate.

11. The Line tab allows you to change the Width (thickness) of the line and its Style (solid, dashed, and so forth). The Symbol tab allows you to put markers at the locations of the data points. You can change their size (Width and Height), Style (none, circle, star, and so forth), and Color.
12. The general properties of the graph are set on the second page of the wizard. Click Next to proceed to this second page.

Related Topics

Published 6/7/2010