Time-Based Variance

About the narrative

Details covered in the analysis

The length of the narrative and the level of detail it includes depends on which narrative length option is selected in Step 3.

For example, when Important things is selected, variance analysis of the measure is performed based on a threshold parameter, the value of which is selected by the user to be applied across all levels of drilldown. Two types of thresholds are supported: Top-N and Coverage. (See Configuration options for details.) When Summary is selected, only the main driver is described. When Tell me everything is selected, all drivers and offsets are described.

The narrative will also include some or all of the following:

  • an introductory section summarizing the key trends, drivers and offsets for the measure (e.g. Profit). For example:

  • for the highest-priority dimension (e.g. Product), a section for each instance of that dimension (e.g. Nutrali), drilled down by up to two other dimensions (e.g. Segment and Country), which highlights the most significant insights. For example:



    The order of drilldown is determined by the order of dimensions set in Step 1.



Data requirements

All NLG Apps have the same data requirements relating to supported formats and field names. See the NLG Apps Data requirements topic for details.

In addition, each app has specific data requirements:

If your data selection and configuration do not meet the specific requirements for a particular app, the app is grayed out and disabled in the wizard. In this example, the Describe a Pie Chart app has been disabled:


Dimensions and measures

This app can analyze:

  • one time dimension, up to three non-time dimensions, and one measure.

Minimum requirement: one time dimension and one measure.


The time dimension must be one of the following date fields:

  • Date

  • Month

  • Quarter

  • Year

For each time dimension, the Entity Type field must be set to DateTime in Step 1 of the wizard.


Aggregation and entity types

Not all combinations of aggregation and entity types are supported for measures. The Time-Based Variance app can analyze the following combinations:



Aggregation types are set in Power BI. Note that Power BI may automatically set the aggregation type of a calculated measure to Don't summarize.

Entity types and other data attributes are set in Step 1 of the Arria for Power BI wizard.



Configuration options

The following options are available to configure:





Select the measure you want to analyze.

Default: first measure listed in Step 1.



Select a time period to analyze. The time dimensions in your data selection must include the period you select here — either as a Date field, or as a Day, Month, Quarter, or Year field.

Default: Month.



Specify how you would like measures to be compared (e.g. Latest vs. previous).

Default: Latest vs. previous.


Entity Selection

Top: Limit the number of drivers and offsets described in your narrative to the top ‘x’ contributors. E.g., “The top three performing regions were…”.

Default: 1.

Coverage: Report on only those drivers and offsets that contributed to a certain percentage of the variance.

Default: 50%.


This option is applied only when Summary and Important things is selected in Step 3.