[Gretl-users] Re: Retrieve day of easterday() as proper integer

Am 08.05.20 um 14:30 schrieb Allin Cottrell: > On Fri, 8 May 2020, Artur Tarassow wrote: > >> I've stumbled over this weird thing trying to retrieve the day of Easter >> Sunday applying the easterday() function as shown in the help text. >> >> However, it seems that scalar "d" is not a proper integer as trying to >> restrict the sample to a single day fails with the error message "No >> observations would be left!". Replacing "d" in the "smpl" command by 5 >> works though. This is using latest git on Ubuntu 19.10. >> >> <hansl> >> clear >> set verbose off >> nulldata 200 >> setobs 7 2015-01-01 --time-series >> >> series year, month, day >> isoconv($obsdate, &year, &month, &day) >> >> scalar e = easterday(2015) >> scalar m = floor(e) >> scalar d = 100*(e-m) > [...] > > Adding at this point > >   printf "4.05 = %.15f\n", 4.05 >   printf "d = %.15f\n", d >   eval d == 5 > > reveals > >   4.05 = 4.050000000000001 >   d = 4.999999999999983 >   0 > > So round() will take d to 5, but not floor(). Hansl doesn't do integer > arithmetic -- and couldn't in this case anyway since e = 4.05, coding for > the 5th of April. > > It seems to me easterday() would be better returning a 2-vector holding > month and day. As things stand you have to use round() on the day, or take > this approach: > > edate = sprintf("%.2f", easterday(2015)) > scalar m, d > sscanf(edate, "%d.%d", m, d) > eval d == 5 # gives 1 Thanks for your alternative approach, Allin. Do you think your suggestion is more reliable compared to the application of round() in this case, or are there some edge-cases where round() may fail here? I've tried round() here for a several years and it seems to work properly.