You can create a baseline to use for anomaly detection. You must have at least a week’s worth of data before you can create a baseline.
Click the desired dashboard under the dashboard heading.
Click the option displayed in the Compare to field.
or
Click Show dashboard details.
Click Create baseline.
Read the confirmation message, then click Create.
After the baseline is created if you want to update the baseline with more amount of data then you can click Regenerate baseline.
After the baseline is created, you can use it to create an anomaly definition as described in Configuring Anomaly Detection.