Whether adding a chart to a dashboard, or creating a chart using Metrics Explorer, the chart-definition interface is nearly identical.
This page discusses the View options tab in the chart-definition interface, which lets you specify how data is presented in the chart. In addition, it covers the options for how the data is displayed on the chart (for example, using lines). This is not configured on the View options tab, but from a pull-down list above the chart. See Chart type for more information.
The following screenshot shows the View options tab from a chart-configuration page:
The View options lets you choose the following visual aspects of your chart, each of which is covered on this page:
- Chart mode lets you choose an alternate to the default chart appearance.
- Threshold lets you place a visual reference line on a chart.
- Compare to Past lets you overlay older data on the chart.
- Log scale of the Y-axis lets you change the presentation of the Y-axis.
For information on the Metrics tab, see Selecting Metrics.
Display modes for charts
Charts provide multiple viewing modes, though not all of them may be available for every chart. For a given chart, the possible modes are:
ColorStatisticsX-RayOutlier
Color mode is the default, and it is the display mode you most frequently encounter. However, not all other modes make sense for all charts. For example, X-ray mode does not apply to bar charts.
When configuring a chart, you can set the view mode for that chart. For a chart on a dashboard, this view mode is usually a default, and you can you can change the view mode for a given chart from the dashboard. A dashboard chart currently in color, statistics, or X-ray mode can be viewed in any of the other applicable modes.
Outlier mode is set when a chart is defined; it does not appear on the controls to change the viewing mode of a chart on a dashboard, as seen in the following screenshot:
When defining a chart, the mode is set by using the Chart mode pull-down on the View options tab, as shown in the following screenshot:
Color mode is the default, but statistics, X-ray, and outlier modes are very useful for certain applications. The following sections describe when these alternate modes are useful.
For comparison in the subsequent sections, the following screenshot shows a chart in color mode:
Statistics mode
Statistics mode displays common statistical measures for the data in a chart.
When you select statistics mode, the chart displays a banner that shows the maximum and minium values as well as a measure of similiarity.
The following screenshot shows the chart in statistics mode:
For charts on a dashboard, the original legend is replaced with a legend consisting of time series that represent various statistics, like mean, standard deviation, and others.
X-ray mode
X-ray mode displays all the graph lines with a translucent gray color. Each line is faint, and where lines overlap or cross, the points appear brighter. Therefore, X-ray mode is most useful on charts with many lines. Overlapping lines create bands of brightness, which indicate the normal behavior within a metrics group.
You can use X-ray mode to see the central tendencies and outliers in dense graphs. For example, if you are looking at CPU utilization across a cluster of machines serving the same data in X-ray mode, you would expect to see a band around the average CPU utilization for the cluster. That band shows how the average ranges and can indicate whether the cluster is over- or under-provisioned. You can also use X-ray mode to identify servers that are not operating optimally.
The following screenshot shows a chart in X-ray mode:
Outlier mode
It is possible to create charts that display a large number of time series. A single metric may include many time series, and if a chart displays multiple metrics, it is easy to end up with a lot of data on the chart. In many cases, a large number of lines on a chart can obscure the interesting ones.
In addition, charts with lots of lines are less responsive than charts with fewer lines, especially when the chart is displaying data from longer time ranges.
Outlier mode shows you the anomalous lines on the chart rather than the highly representative ones. This reduces the number of lines on the chart and helps keep individual charts both responsive and intelligible.
Outlier mode is set when you build the chart, either when by adding a new chart to a dashboard or by using Metrics Explorer. Charts already on a dashboard cannot be switched into this mode. You can select the number of time series to show, whether you want extreme high or low values, and the method by which the time series are ranked, as seen in the following screenshot:
You also can change a noisy chart to outlier mode by clicking the link in the banner the chart displays when there are too many lines to be useful:
By default, a chart in outlier mode shows the top 3 lines, ranked by mean. A small annotation on the chart describes the display criteria.
Threshold
The Threshold option creates a horizontal line from a point on the Y-axis. The line provides a visual reference for the chosen threshold value.
To create a threshold line:
- Check the Threshold option.
- Set the desired value for the threshold in the field under the option name.
The following screenshot shows the setting of a threshold:
The following screenshot shows a chart with a threshold line:
Compare to Past
The Compare to Past option lets you select a time range from the past by specifying a number of hours, days, or weeks. The data from that time range is then superimposed as a dotted line over the current data on a line chart. The legend also shows past and present values.
Compare to Past is not applicable to chart types other than line charts.
To show older data on the chart:
- Check the Compare to Past option.
- Specify how far back in the past to go:
- The period (hours, days, weeks)
- The number of periods
The data superimposed on your chart is for the same display period as your chart, but from the specified time in the past. For example, if your chart is showing data from between 10:00am and 11:00am, and you specify data from 2 weeks ago as 'past data', you will see data collected between 10am and 11am on the day two weeks past.
If there is no data available from the requested period, you will not see any change on the chart.
The following screenshot shows a request for data from 2 weeks ago:
The following screenshots show the same chart with and without the data from 2 weeks ago.
Without past data:
With past data and one time series highlighted:
Log scale on Y-axis
The Log scale on Y-axis option rescales the chart's Y-values logarithmically. This rescaling is useful when values cluster tightly within a small range. Check to box to enable this option, and uncheck it to disable it.
The following screenshots show the same chart with the default Y-axis and with a log-scaled Y-axis.
Default Y-axis:
Log-scaled Y-axis:
Chart type
In addition to the options on the View options tab, you can also
specify the how the chart graphs the data. The default style is a line
chart, but other styles, stacked bar and stacked area, are also available.
To change the display style of a chart, select the desired type from the
pull-down menu located just above the chart on the upper left. The pull-down
shows the current style, which is most typically Line.
The following sequence of screen shots shows the same chart using each of the three display styles.
There are two types of line charts and one bar chart. The line charts are higher resolution than bar charts; this is due to the alignment period used.
Standard line chart:
Stacked area chart:
Stacked bar chart:
The complete set of options is not always available; for example, bar
charts are not appropriate for data being viewed in
X-ray mode. If you choose a chart type that is incompatible
with a chosen chart mode, the chart mode reverts to Color.