Automatic detection of anomalies

This is a deceptively large change, hidden away on the Analytics card for a line chart. 

What anomalies are and how they work

Suppose you have some time-series data:

A line chart showing sales by day across 2020.

You can apply anomalies to highlight questionable data points (any other readers remember the Primeval TV series at this point?):

The anomalies are pretty much where you'd expect them to be.

You can then click on an anomaly to see an explanation of why it might be occurring:

A summary of the anomaly, followed by a list of possible explanation (not shown here).

Starting to show anomalies

To show anomalies, first select a line chart visual with a time axis:

This visual shows total sales by date for 2020.

On the Analytics card, expand the Anomalies card:

Select the angry Pac-Man symbol, then expand Find anomalies at the bottom of the list of properties.

Choose to add anomaly markers:

Click on the Add link to show any anomalies.

The lower the sensitivity, the less "anomalies" you'll detect:

The default 70% sensitivity	Applying 40% sensitivity

Formatting anomalies

You can format your anomalies (and the area showing where normally data would be expected to occur) in a fairly obvious way.  For example, these settings:

Some fairly tasteless formatting!

Would give this line chart:

The green expected area was a particularly bad idea.

Explaining anomalies

If you want to see more details about a particular anomaly, select it:

Here I've gone for the biggest anomaly - the figure for 15th April 2020, which is over twice what you would expect the highest value to be given the other data.

This displays an Anomalies pane;

An explanation of what's happening, followed by a list of possible explanations.

I'd love at this point to show you a list of the explanations, but instead this is what I see:

The message I get at this point.

Instead, I'll switch to Microsoft's explanation of how to work with anomalies at this point, to show the sort of thing you should get:

You can click on each explanation to see a chart explaining it in more detail.

Adding explanatory fields

Explanations consider all possible fields, but you might want to limit the scope of your investigation (for our example, you might theorise that the anomaly will be explicable by reference to the town and/or product data):

Here I've dragged the TownName and ProductName fields onto the Explain by card, to try to explain my anomalies in those terms only.