If you look closely at your weekly graph, the curve does not go to zero. Instead, it's missing. That's the effect of the null values.
Same with monthly, but more obvious. >From what I'm seeing, your results reflect how SQL handles averages. On Sat, Jun 3, 2023 at 7:11 PM 'Peter Fletcher' via weewx-user < [email protected]> wrote: > I would not expect the standard SQL behavior (ignoring nulls and averaging > the rest of the values) to result in what I am seeing in the graphs, but > you are probably right that I am going to have to define a specialty > aggregation. > > On Saturday, June 3, 2023 at 8:10:26 PM UTC-4 Tom Keffer wrote: > >> WeeWX uses a SQL statement to calculate the averages. SQL ignores any >> nulls in an aggregate interval. So, if there is nothing but nulls in an >> interval, the result will be null, not zero. >> >> Null values signify unknown values, not zero. I didn't follow the >> discussion of your service, but if you can't change it to store zero when >> the value is, well, zero, then you'll have to define your own specialty >> xtype aggregations, which treats null as a zero, perhaps by using the SQL >> function IFNULL(). >> >> Instructions on defining custom xtype aggregations: >> https://github.com/weewx/weewx/wiki/xtypes#calculating-aggregates >> >> >> On Sat, Jun 3, 2023 at 4:39 PM 'Peter Fletcher' via weewx-user < >> [email protected]> wrote: >> >>> For reasons discussed elsewhere, I have a user service which saves >>> nulls. rather than zeros to the archive records for UV and solar radiation >>> values during the night. Daily and weekly graphs continue to look as they >>> should (with the daytime tracings arising from at or very near to the zero >>> axis). On the monthly graphs, however, the tracings do not touch the zero >>> axis at either end of the daytime peak, I am guessing that, in calculating >>> averaged data points for the longer term graphs, weewx is treating the >>> average of any group of values that contains a null value as null. There is >>> some logic to this, but the results are unhelpful in this case. Am I right >>> about the cause of the problem, and is there a workaround for it? >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "weewx-user" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/weewx-user/aff03e49-1c45-4383-bc80-a3db9425ac8fn%40googlegroups.com >>> <https://groups.google.com/d/msgid/weewx-user/aff03e49-1c45-4383-bc80-a3db9425ac8fn%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- > You received this message because you are subscribed to the Google Groups > "weewx-user" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/0f0dab2d-ad9f-4297-a5db-c87c23981ae8n%40googlegroups.com > <https://groups.google.com/d/msgid/weewx-user/0f0dab2d-ad9f-4297-a5db-c87c23981ae8n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/CAPq0zED4swoDhXmNPNF%3DVfMaXF8JDHTRj-9c-WO5U_OoqFGy%3DA%40mail.gmail.com.
