View data in a scatter plot

Scatter plots show value pairs. As in a geometric coordinate system, every data point in scatter plot must have an X value that determines its horizontal position as well as a Y value that determines the vertical position. On a regular trend, there is no such thing as an "X value" that corresponds to the Y value of a tag; instead, the horizontal position of a tag’s value on the chart is determined by the value’s time stamp.

On a scatter plot, however, both the X and the Y values must be supplied as tag data. Therefore, you must assign an X axis tag to every tag that you want to view in the scatter plot.

Tags without a corresponding X axis tag are visible in the Tag List, but not in the chart. For more information on how X and Y values are matched, see How are value pairs matched?

To configure a scatter plot

1. Click the New Chart toolbar button. A new trend chart appears.

2. On the Chart menu, in the Layout group, select Scatter.

   The chart switches into scatter plot mode.

3. Add tags to the chart by double-clicking them in the Tag Picker or dragging them onto the Tag List. For more information on the Tag Picker, see Tag Picker.

   You must add all tags that you want to use as X or Y axis tags. Note the following:

   • One tag can serve as the X axis tag for multiple other tags.

   • If you want to view the same tag against different X axis tags, add it to the Tag List multiple times.

   • While you can add string or event tags, they serve no purpose in a scatter plot. Therefore, these tags are automatically marked as hidden.

4. Specify a time period for the chart using the time toolbar.

5. Assign an X axis tag to every tag that you want to view in the scatter plot:

   1. Double-click the tagname in the Tag List. The <ServerName:Tagname> dialog box appears with the General tab selected.

   2. In the X axis Tag List, click the name of the tag that you want to use as the X axis tag for this tag. To remove an existing X axis tag association, click the blank entry instead.

   3. Configure other tag options as required. For more information, see Configuring Trend Options for a Tag.

   4. Click OK.

   Data for the X/Y tag pairs is retrieved for the specified time period and plotted in the chart. The oldest value pair appears as a triangle-shaped point, and the latest value pair as a diamond-shaped point.

   Tags that do not have an X axis tag assigned to them are shown in italics at the end of the Tag List.

To quickly assign an X axis tag to a tag

If you do not need to configure any other tag settings, you can use the following steps to quickly assign an X axis tag to a tag that you want to display in a scatter plot (the Y axis tag).

6. Add the Y axis tag to the chart.

7. With the Y axis tag selected in the Tag List, drag the X axis tag from the Tag Picker onto the X axis of the chart.

Alternatively, use these steps:

8. Add the X and Y axis tags to the chart.

9. In the Tag List, click the X axis tag’s name and drag it onto the X Axis Tag column of the Y axis tag.