This is the total number of unique subscribers who are seen in only one locality in each time interval.
You can find the SQL code for producing this aggregate in count_subscribers_single_locality.sql.
The query count_subscribers_single_locality_per_day is a standalone query which can be run by itself to produce the aggregate.
The first time you run this, you will need to include a timespan of data that includes the period before any mobility restrictions were enforced in your country, or before the first cases of COVID-19 were reported in your country. This is so that you can establish what ‘normal’ baseline behaviour looks like, and then see how this behaviour changed. We recommend that you include at least two weeks of ‘normal’ baseline data (i.e. the two weeks immediately before the announcement of restrictions or the outbreak), and preferably four weeks.
Once you have this baseline data, you can then run the count_subscribers_single_locality_per_day query once every day, only looking at a single day’s data (yesterday).
We recommend that you also modify the count_subscribers_single_locality_per_day query to count single-locality subscribers per week (see Note on calculating aggregates over multiple time intervals). When aggregating by week, take care to specify a date range that includes entire weeks (e.g. the inbuilt extract(WEEK FROM ...) function in Postgres assigns a number to each week, with weeks starting on Monday and ending on Sunday).
This can be useful in combination with other aggregates. For example, counts of static subscribers per locality can be scaled using subscriber counts to get proportions of subscribers per locality who are adhering to mobility restrictions.