Allow 7-day averages

[marcowitz]

This tools is one of the best visualizations on the official case data out there. Congratulations 🎉

It would be really cool, if instead of the single values, one could also look at 7-day averages. Main reason for this is, that relevant data (such as daily confirmed cases) are very noisy (no lab work on weekends, etc.). This is why many analysts and even law-makers now consider the 7-day rolling average as the more relevant number for comparisons and to detect trends.

[boogheta]

Hi and thanks fo your feedback. The option actually already is there, although probably too discrete as you're not the first one to ask for it! :) Whenever you select "daily", a small icon with a line and two arrows appears to let you enable such 7-day average mode. Enjoy! :)

[marcowitz]

I think something is wrong with the 7day moving average:

See here the 7-day averaged data on Sweden from 2 days ago:

and here the non-smoothend version:

The smoothened version does not really seem to show the 7-day moving average. If it did, it should also not change with new data (because it only looks into the past). But if I look at sweden today, this is the smoothened curve:

It seems to me that the average is not really "rolling". In the sense of looking for each day into the past 7 and displaying their average.

[RouxRC]

Here's how it's computed: https://github.com/boogheta/coronavirus-countries/blob/master/js/corona.js#L856 I'm open to suggestions but I don't see how it should be done differently: if you want to display values for the last 3 days, these can only account for the mean of the last 4, 5 and 6 days to be consistent, which results necessarily in these kind of temporary decrease with reportings such as Sweden with a peak each week catching up on the figures from the week-end.

[marcowitz]

At least in Germany official 7-day rolling average numbers are calculated always looking backwards (see: https://www.sueddeutsche.de/muenchen/coronavirus-sieben-tage-inzidenz-berechnen-1.4909107). Meaning that the rolling average value on day X is the one of the past 7 days of day X (including day X, if the data for day X is final). This ensures that the value of the 7-day rolling average is static and will not change when new data comes in.

For the code it would probably mean something like: return d3.mean(values[c.id][cas][typVal].slice(Math.max(0, idx - 7), idx));

[boogheta]

Thanks for your feedback, that would be the way to do so indeed. But I'm a bit split about such a change. It would indeed avoid the varying last days effect my method causes, but it would also:

• forbid to display data for the first 7 days of the datasets
• make the data displayed for a specific date not representative of the average values at this date but more of the past week I need to think about it more and experimenting a bit before deciding