Configure legends

This document describes how to work with chart legends. The legend looks like a table positioned adjacent to the graph. By default, the legend on a dashboard is configured to show only the colored dots that correspond to lines in the graph. The following screenshot shows a chart on a dashboard with the default legend:

For charts on dashboards, you can also expand the legend to view more details, such as configurable data columns and a Valuecolumn. The Valuecolumn displays the values for the metric being charted, and other columns display the values of chosen metric or resource labels. The dashed bar on the chart indicates the time for which values are displayed.

To access resource-specific dashboards or to apply temporary filters to a dashboard, use the more_vert Actions for this timeseriesmenu in an expanded legend.

Show and hide legends

Legends for charts that display multiple metric types might be difficult to interpret. By default, the legend columns are selected from the metric and resource labels for the charted metric type. When a chart has multiple metric types, the result is that a specific legend column might not be meaningful for a specific time series.

• Example: A chart displays the number of bytes written to and the number of bytes read from virtual machine (VM) instances. Assume that the bytes-read data is filtered to the us-central1-a zone. The legend includes a zone column, and the values in that column might be different than us-central1-a . The reason is that the bytes-written metric type contains a zone label and that metric data wasn't filtered by zone.

• Example: A chart displays the number of bytes written to VM instances and the CPU usage for those instances. The legend contains columns for the disk type and storage type. However, the values for those labels are empty for time legend fields. The reason is that the CPU usage metric type doesn't support those labels.

Select legend columns

To change the columns that appear in the legend, expand the legend then click view_column Legend columns. Clicking the button brings up a configuration panel. This panel lists the metric and resource labels available to display as columns. Required columns have disabled checkboxes. The following screenshot shows the Columnsbutton and the configuration panel for a particular legend:

When the chart is initially created, the system heuristically chooses a set of labels to show by default. You can select or clear labeled columns. The entries for required columns, most typically Value, are disabled and can't be cleared. When you change the configuration, you must have at least one metric or resource label selected.

The legend displays a scrollbar when it has many columns to display, and paginates the legend when there are many rows to display. The following screenshot illustrates a legend with a scrollbar, and arrows for navigating through the pages:

Sort legend rows

You can sort the rows of the legend by any of the columns. Rows can be sorted into ascending or descending order. To sort a row, click the header. The most recently sorted column displays an arrow indicating the sort order. The following screenshot shows a legend that has been sorted by zonein descending order:

Understand legends in "Compare to Past" mode

When you use Compare to Pastmode on a chart, the legend is modified to include a second “values” column. The current Valuecolumn becomes Today, and the past values column is named appropriately—for example, Last Week. The following screenshot shows a legend for a table comparing current data to that of the last hour:

Configure the name of a legend column

The Legend Aliasfield lets you customize a description for the time series on your chart. These descriptions appear on the tooltip for the chart and on the chart legend in the Namecolumn. By default, the descriptions in the legend are created for you from the values of different labels in your time series. Because the system selects the labels, the results might not be helpful to you. To build a template for descriptions, use this field.

You can enter plain text and templates in the Legend Aliasfield. When you add a template, you add an expression that is evaluated when the legend is displayed.

To add a legend template to a chart, do the following:

1. In the Displaypane, expand expand_more Legend Alias.
2. Click add Display template variable suggestionsand select an entry from the menu. For example, if you select zone , then the template ${resource.labels.zone} is added.

For example, the following screenshot shows a legend template that contains plain text and the expression ${resource.labels.zone} :

In the chart legend, the values generated from the template appear in a column with the header Nameand in the tooltip:

You can configure the legend template to include multiple text strings and templates; however, the display space available on the tooltip is limited.

Access resource-specific dashboards