Thanks Tom! I love Weewx and get a kick out of playing with the data. My biggest variance here in Springfield Illinois was 4.4 degrees. On 4/21/21 at 12:15pm i went from 49.1 to 56.3 then fell back to 54.7. No rain that day, just clouds and sun I guess. Breezy.
Walt On Sunday, October 3, 2021 at 8:39:09 PM UTC-5 tke...@gmail.com wrote: > Wow! Some serious SQL fu! > > Very nice. > > On Sun, Oct 3, 2021 at 12:20 PM wfs...@gmail.com <wfs...@gmail.com> wrote: > >> Here's an updated query that does better checking and it can delete the >> rows or update the temperatures. Test it out on a copy of your database >> first. This works for sqlite. Don't know about others. >> >> Walt >> >> On Sunday, October 3, 2021 at 6:48:23 AM UTC-5 anc...@gmail.com wrote: >> >>> Exactly. Is there a way to consider only cases such as +0, -10, +0 >>> (i.e. spikes) and not those like +0, -6. -8 ? >>> Meanwhile I thank you for your precious help. >>> Andrea >>> >>> Il giorno giovedì 30 settembre 2021 alle 23:03:35 UTC+2 wfs...@gmail.com >>> ha scritto: >>> >>>> Just a reminder, this delete query will delete all situations where the >>>> criteria is met. Some of these situations are legit, temps can change >>>> rapidly. You want to make sure it's going to delete only the records you >>>> want before running it. There are probably some enhancements that can be >>>> made to the query to find more obvious spikes. Something like +0, -10, +0 >>>> might be a spike, whereas +0, -6. -8 is not, the temp is just falling fast. >>>> >>>> On Thursday, September 30, 2021 at 1:11:05 PM UTC-5 wfs...@gmail.com >>>> wrote: >>>> >>>>> Well, make sure you back up your database before you try to delete >>>>> anything in case this goes wrong. I would >>>>> >>>>> 1. Stop weewx >>>>> 2. Make a copy of the database >>>>> 3. Execute the delete SQL >>>>> 4. Run the original query again to see if things are OK >>>>> 5. Rebuild weewx dailies >>>>> 6. Start weewx >>>>> >>>>> Hopefully I'm not forgetting anything. >>>>> >>>>> I'm attaching SQL to delete the spiked records. You will have to >>>>> change the database name in the .open statement to the db you want to >>>>> change. You may need to run sqlite3 with sudo in order to delete records. >>>>> >>>>> I thought a better solution would be to update the spiked temp with an >>>>> average of the readings surrounding the spike, but I'm having trouble >>>>> coming up with the SQL to do that. >>>>> >>>>> Walt >>>>> On Thursday, September 30, 2021 at 9:41:17 AM UTC-5 anc...@gmail.com >>>>> wrote: >>>>> >>>>>> Thank you Walt, this script works fine! in fact it highlighted that >>>>>> spike in my graph: >>>>>> >>>>>> DT datetime temp temp_prior >>>>>> temp_next variance d_back d_forw >>>>>> ------------------- ---------- ---------------- ---------------- >>>>>> ---------------- ---------- ------------------ ---------------- >>>>>> 2021-09-30 04:15:00 1632968100 19.2970370370371 19.3363567649282 >>>>>> 14.5003779289494 2.38 0.0393197278911508 4.79665910808766 >>>>>> >>>>>> (I added two columns d_back = |t1-t2| and t_forw = |t1-t3|) >>>>>> Now, I need to delete the wrong record: in this case, it is t3 >>>>>> (d_forw = 4.8). How can I automatically find it and then remove? >>>>>> Unfortunately I don't know the sql language and I can't complete the >>>>>> script >>>>>> myself. >>>>>> >>>>>> Thank you very much, >>>>>> Andrea >>>>>> Il giorno giovedì 30 settembre 2021 alle 15:27:37 UTC+2 >>>>>> wfs...@gmail.com ha scritto: >>>>>> >>>>>>> Here's a query using the "join a table to itself" method if you >>>>>>> don't have the LAG function. It prints observations that are outside >>>>>>> the >>>>>>> average of the surrounding observations by 2+ degrees. I get about 30 >>>>>>> observations this year and I think it's legit. Although I don't get >>>>>>> spikes >>>>>>> in my data, I do use a 15 minute interval and my station is closer to >>>>>>> the >>>>>>> ground than it should be. A lot can happen in 15 minutes and my temp >>>>>>> graph >>>>>>> is always kinda wiggly. >>>>>>> >>>>>>> Caveat Emptor on the attached query. You could modify it to delete >>>>>>> or update the offending rows instead of printing them out. >>>>>>> >>>>>>> Walt >>>>>>> >>>>>>> >>>>>>> On Thursday, September 30, 2021 at 7:52:41 AM UTC-5 tke...@gmail.com >>>>>>> wrote: >>>>>>> >>>>>>>> Yes, it's possible, but it's not a simple SELECT statement. For >>>>>>>> example, this query will return all rows where the temperature >>>>>>>> difference >>>>>>>> between adjacent rows is greater than 1 degree: >>>>>>>> >>>>>>>> >>>>>>>> *SELECT g.* FROM (SELECT dateTime, >>>>>>>> datetime(dateTime,'unixepoch','localtime'), LAG(outTemp) OVER (ORDER >>>>>>>> BY >>>>>>>> dateTime) AS prev_outTemp, outTemp FROM archive) AS g WHERE >>>>>>>> ABS(g.outTemp-g.prev_outTemp) > 1;* >>>>>>>> >>>>>>>> For my own database, this returns >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> *1192323300|2007-10-13 17:55:00|64.099998|63.01192382100|2007-10-14 >>>>>>>> 10:15:00|51.900002|53.01192756800|2007-10-18 >>>>>>>> 18:20:00|44.700001|46.7000011192757100|2007-10-18 >>>>>>>> 18:25:00|46.700001|49.51192757400|2007-10-18 18:30:00|49.5|47.400002* >>>>>>>> ... >>>>>>>> >>>>>>>> You would then need to arrange to delete those specific timestamps. >>>>>>>> >>>>>>>> The select statement will only work with modern versions of sqlite, >>>>>>>> which have the LAG() function. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Thu, Sep 30, 2021 at 3:35 AM anc...@gmail.com <anc...@gmail.com> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> Hi there, >>>>>>>>> I need to remove some temperature spikes from my weewx.sdb >>>>>>>>> database. I know this has been already asked many times, but my case >>>>>>>>> is >>>>>>>>> different. I need to delete spikes in which the values are >>>>>>>>> climatically >>>>>>>>> acceptable: so, it is not sufficient to give (temperature is intended >>>>>>>>> in °C) >>>>>>>>> >>>>>>>>> echo "delete from archive where outTemp < -6;" | sudo sqlite3 >>>>>>>>> /home/weewx/archive/weewx.sdb >>>>>>>>> >>>>>>>>> for solving the problem. In my case, the spike was about 16°C when >>>>>>>>> temperature was about 20°C (see the graph below) >>>>>>>>> [image: daytempdew.png] >>>>>>>>> What I need to do is something like: DELETE if Δt = 300 AND |ΔT| >>>>>>>>> > 5, where >>>>>>>>> Δt is time difference (in seconds, I chose 300 because my archive >>>>>>>>> interval is 5 minutes) and ΔT is the temperature difference in that >>>>>>>>> time >>>>>>>>> bin. >>>>>>>>> In other words I am thinking about using a differential approach. >>>>>>>>> It seems to me that this can be the only solution, is this possible >>>>>>>>> with >>>>>>>>> sqlite3? >>>>>>>>> Thank you, >>>>>>>>> Andrea >>>>>>>>> >>>>>>>>> -- >>>>>>>>> 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 weewx-user+...@googlegroups.com. >>>>>>>>> To view this discussion on the web visit >>>>>>>>> https://groups.google.com/d/msgid/weewx-user/32298c8c-6d93-4a80-8b9e-29fdcc181c8an%40googlegroups.com >>>>>>>>> >>>>>>>>> <https://groups.google.com/d/msgid/weewx-user/32298c8c-6d93-4a80-8b9e-29fdcc181c8an%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 weewx-user+...@googlegroups.com. >> > To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/a3b5661f-58d6-4c17-8ce2-4c55ca620eb1n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/weewx-user/a3b5661f-58d6-4c17-8ce2-4c55ca620eb1n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. 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