Tag History Average

Philip_Knowlton · December 5, 2025, 3:04am

Hello all,

I’m working on some tag history queries and I’m curious why I’m seeing a discrepancy between when I have the queryTagHistory function aggregate the simple average and when I get the values and calculate the simple average myself. It’s a small difference, but I don’t understand what might be causing it.

The script that I’m running:

path = ['[default]316/Hydro/Lane 1/DRIVE_OUTPUT_FREQ']
startDate = system.date.addHours(system.date.now(), -8)
endDate = system.date.now()
aggregationMode = 'SimpleAverage'
average = system.tag.queryTagHistory(paths=path, startDate=startDate, endDate=endDate, aggregationMode=aggregationMode, returnSize=1)
dataset = system.tag.queryTagHistory(paths=path, startDate=startDate, endDate=endDate)
data = system.dataset.toPyDataSet(dataset)

pyaverage = system.dataset.toPyDataSet(average)

data
sums = 0
count = 0
for item in data:
    sums += item[1]
    count += 1

calcAvg = sums/count
pyAvg    = pyaverage[0][1]
difference = abs(calcAvg - pyAvg)
'Calculated Avg = ' + str(calcAvg)
'Simple Average = ' + str(pyAvg)
'Difference = ' + str(difference)

This returns the following every time (I’m including the data from the dataset as well):

> [[Thu Dec 04 13:56:44 EST 2025, 46.98334884643555], [Thu Dec 04 13:59:27 EST 2025, 46.27568054199219], [Thu Dec 04 13:59:30 EST 2025, 47.99862289428711], [Thu Dec 04 13:59:36 EST 2025, 46.52957534790039], [Thu Dec 04 14:03:52 EST 2025, 47.79416275024414], [Thu Dec 04 14:03:55 EST 2025, 45.62660598754883], [Thu Dec 04 14:04:04 EST 2025, 47.362735748291016], [Thu Dec 04 14:06:43 EST 2025, 46.46141052246094], [Thu Dec 04 14:07:44 EST 2025, 47.132850646972656], [Thu Dec 04 14:08:59 EST 2025, 45.69489669799805], [Thu Dec 04 14:09:02 EST 2025, 47.708099365234375], [Thu Dec 04 14:09:29 EST 2025, 46.661434173583984], [Thu Dec 04 14:16:55 EST 2025, 47.59531784057617], [Thu Dec 04 14:17:01 EST 2025, 45.718021392822266], [Thu Dec 04 14:17:04 EST 2025, 47.47039031982422], [Thu Dec 04 14:17:07 EST 2025, 45.97634506225586], [Thu Dec 04 14:17:25 EST 2025, 47.48807907104492], [Thu Dec 04 14:17:46 EST 2025, 46.2236213684082], [Thu Dec 04 14:18:01 EST 2025, 46.61347961425781], [Thu Dec 04 14:19:32 EST 2025, 46.18155288696289], [Thu Dec 04 14:20:14 EST 2025, 47.334739685058594], [Thu Dec 04 14:20:38 EST 2025, 46.05891036987305], [Thu Dec 04 14:20:41 EST 2025, 47.69902420043945], [Thu Dec 04 14:20:44 EST 2025, 46.01299285888672], [Thu Dec 04 14:20:56 EST 2025, 47.299495697021484], [Thu Dec 04 14:21:38 EST 2025, 47.73240661621094], [Thu Dec 04 14:21:41 EST 2025, 45.700714111328125], [Thu Dec 04 14:21:50 EST 2025, 47.46564865112305], [Thu Dec 04 14:21:53 EST 2025, 45.56600570678711], [Thu Dec 04 14:21:56 EST 2025, 47.967002868652344], [Thu Dec 04 14:22:08 EST 2025, 47.20979309082031], [Thu Dec 04 14:24:21 EST 2025, 47.25664520263672], [Thu Dec 04 14:27:06 EST 2025, 47.49977493286133], [Thu Dec 04 14:27:21 EST 2025, 46.54741668701172], [Thu Dec 04 14:28:18 EST 2025, 47.5872917175293], [Thu Dec 04 14:28:30 EST 2025, 46.510684967041016], [Thu Dec 04 14:29:19 EST 2025, 47.36219787597656], [Thu Dec 04 14:30:25 EST 2025, 46.23542785644531], [Thu Dec 04 14:30:52 EST 2025, 46.896881103515625], [Thu Dec 04 14:34:17 EST 2025, 47.143253326416016], [Thu Dec 04 14:36:15 EST 2025, 45.66246795654297], [Thu Dec 04 14:36:18 EST 2025, 47.549800872802734], [Thu Dec 04 14:36:30 EST 2025, 47.21089172363281], [Thu Dec 04 14:37:36 EST 2025, 47.66851043701172], [Thu Dec 04 14:37:39 EST 2025, 45.618839263916016], [Thu Dec 04 14:37:42 EST 2025, 47.774986267089844], [Thu Dec 04 14:37:51 EST 2025, 45.933868408203125], [Thu Dec 04 14:37:54 EST 2025, 47.18854904174805], [Thu Dec 04 14:38:51 EST 2025, 47.06993865966797], [Thu Dec 04 14:40:15 EST 2025, 47.71101379394531], [Thu Dec 04 14:40:18 EST 2025, 45.55598831176758], [Thu Dec 04 14:40:27 EST 2025, 47.09587860107422], [Thu Dec 04 14:41:19 EST 2025, 46.080909729003906], [Thu Dec 04 14:41:22 EST 2025, 47.663814544677734], [Thu Dec 04 14:41:34 EST 2025, 45.50700759887695], [Thu Dec 04 14:41:37 EST 2025, 47.14875793457031], [Thu Dec 04 14:43:04 EST 2025, 46.36251449584961], [Thu Dec 04 14:43:34 EST 2025, 47.67601013183594], [Thu Dec 04 14:44:22 EST 2025, 46.12061309814453], [Thu Dec 04 14:45:25 EST 2025, 47.76698303222656], [Thu Dec 04 14:45:28 EST 2025, 45.96742248535156], [Thu Dec 04 14:45:46 EST 2025, 47.63303756713867], [Thu Dec 04 14:45:55 EST 2025, 47.16328430175781], [Thu Dec 04 14:46:47 EST 2025, 47.93854522705078], [Thu Dec 04 14:46:50 EST 2025, 45.744293212890625], [Thu Dec 04 14:46:53 EST 2025, 48.02195739746094], [Thu Dec 04 14:46:59 EST 2025, 46.00933837890625], [Thu Dec 04 14:47:48 EST 2025, 47.22980499267578], [Thu Dec 04 14:47:51 EST 2025, 45.593719482421875], [Thu Dec 04 14:47:54 EST 2025, 47.13865280151367], [Thu Dec 04 14:48:30 EST 2025, 45.930294036865234], [Thu Dec 04 14:48:36 EST 2025, 48.1173210144043], [Thu Dec 04 14:48:39 EST 2025, 46.48741149902344], [Thu Dec 04 14:51:51 EST 2025, 46.17542266845703], [Thu Dec 04 14:51:54 EST 2025, 48.08400344848633], [Thu Dec 04 14:51:57 EST 2025, 46.09372329711914], [Thu Dec 04 14:52:00 EST 2025, 47.86171340942383], [Thu Dec 04 14:52:09 EST 2025, 46.30685806274414], [Thu Dec 04 14:52:25 EST 2025, 46.582801818847656], [Thu Dec 04 14:54:07 EST 2025, 46.56275177001953], [Thu Dec 04 14:54:25 EST 2025, 47.511985778808594], [Thu Dec 04 14:56:04 EST 2025, 46.298282623291016], [Thu Dec 04 14:56:07 EST 2025, 47.857749938964844], [Thu Dec 04 14:56:10 EST 2025, 45.78828048706055], [Thu Dec 04 14:56:16 EST 2025, 47.134613037109375], [Thu Dec 04 14:59:02 EST 2025, 46.204288482666016], [Thu Dec 04 14:59:05 EST 2025, 47.38050079345703], [Thu Dec 04 14:59:47 EST 2025, 45.833675384521484], [Thu Dec 04 14:59:50 EST 2025, 47.473243713378906], [Thu Dec 04 14:59:53 EST 2025, 45.59413146972656], [Thu Dec 04 15:00:11 EST 2025, 46.945152282714844], [Thu Dec 04 15:01:32 EST 2025, 47.14221954345703], [Thu Dec 04 15:01:38 EST 2025, 46.85291290283203], [Thu Dec 04 15:02:47 EST 2025, 46.00080490112305], [Thu Dec 04 15:03:58 EST 2025, 47.24273681640625], [Thu Dec 04 15:04:22 EST 2025, 46.967262268066406], [Thu Dec 04 15:05:19 EST 2025, 46.39208984375], [Thu Dec 04 15:05:28 EST 2025, 48.311561584472656], [Thu Dec 04 15:05:31 EST 2025, 46.28877258300781], [Thu Dec 04 15:05:43 EST 2025, 47.33297348022461], [Thu Dec 04 15:05:52 EST 2025, 46.99588394165039], [Thu Dec 04 15:10:29 EST 2025, 46.04734802246094], [Thu Dec 04 15:10:38 EST 2025, 48.078895568847656], [Thu Dec 04 15:10:41 EST 2025, 46.27861404418945], [Thu Dec 04 15:11:02 EST 2025, 47.462493896484375], [Thu Dec 04 15:11:14 EST 2025, 46.19480514526367], [Thu Dec 04 15:11:26 EST 2025, 46.45966720581055], [Thu Dec 04 15:14:59 EST 2025, 46.42288589477539], [Thu Dec 04 15:16:48 EST 2025, 47.55547332763672], [Thu Dec 04 15:17:00 EST 2025, 47.09760284423828], [Thu Dec 04 15:21:29 EST 2025, 46.33409881591797], [Thu Dec 04 15:22:23 EST 2025, 47.50423812866211], [Thu Dec 04 15:22:59 EST 2025, 46.62060546875], [Thu Dec 04 15:23:14 EST 2025, 46.576541900634766], [Thu Dec 04 15:24:08 EST 2025, 47.826927185058594], [Thu Dec 04 15:24:14 EST 2025, 45.77653121948242], [Thu Dec 04 15:24:17 EST 2025, 47.597190856933594], [Thu Dec 04 15:24:32 EST 2025, 46.27937316894531], [Thu Dec 04 15:26:29 EST 2025, 47.49794387817383], [Thu Dec 04 15:26:32 EST 2025, 46.04222869873047], [Thu Dec 04 15:26:42 EST 2025, 47.22065353393555], [Thu Dec 04 15:27:21 EST 2025, 45.965152740478516], [Thu Dec 04 15:27:30 EST 2025, 47.45490646362305], [Thu Dec 04 15:28:18 EST 2025, 46.08833694458008], [Thu Dec 04 15:28:24 EST 2025, 46.28999328613281], [Thu Dec 04 15:30:18 EST 2025, 47.436744689941406], [Thu Dec 04 15:30:21 EST 2025, 45.782493591308594], [Thu Dec 04 15:30:30 EST 2025, 47.5121955871582], [Thu Dec 04 15:30:33 EST 2025, 46.13022232055664], [Thu Dec 04 15:31:00 EST 2025, 47.6919059753418], [Thu Dec 04 15:31:09 EST 2025, 46.62355041503906], [Thu Dec 04 15:32:06 EST 2025, 47.36103439331055], [Thu Dec 04 15:32:30 EST 2025, 46.435302734375], [Thu Dec 04 15:32:56 EST 2025, 46.470794677734375], [Thu Dec 04 15:37:08 EST 2025, 47.205909729003906], [Thu Dec 04 15:38:29 EST 2025, 46.2726936340332], [Thu Dec 04 15:38:51 EST 2025, 47.62767791748047], [Thu Dec 04 15:40:51 EST 2025, 45.355125427246094], [Thu Dec 04 15:40:54 EST 2025, 47.64714050292969], [Thu Dec 04 15:41:09 EST 2025, 46.32932662963867], [Thu Dec 04 15:42:36 EST 2025, 47.217891693115234], [Thu Dec 04 15:43:57 EST 2025, 47.09811782836914], [Thu Dec 04 15:47:13 EST 2025, 47.68549346923828], [Thu Dec 04 15:47:16 EST 2025, 45.5410041809082], [Thu Dec 04 15:47:25 EST 2025, 48.07463073730469], [Thu Dec 04 15:47:34 EST 2025, 46.50251770019531], [Thu Dec 04 15:50:02 EST 2025, 48.13511657714844], [Thu Dec 04 15:50:09 EST 2025, 46.63682556152344], [Thu Dec 04 15:51:06 EST 2025, 47.268157958984375], [Thu Dec 04 15:51:18 EST 2025, 46.149375915527344], [Thu Dec 04 15:51:42 EST 2025, 47.597286224365234], [Thu Dec 04 15:52:06 EST 2025, 46.56608963012695], [Thu Dec 04 15:52:21 EST 2025, 47.99241256713867], [Thu Dec 04 15:52:24 EST 2025, 45.941837310791016], [Thu Dec 04 15:52:27 EST 2025, 47.990638732910156], [Thu Dec 04 15:52:42 EST 2025, 46.07080078125], [Thu Dec 04 15:52:45 EST 2025, 47.80990982055664], [Thu Dec 04 15:52:48 EST 2025, 45.43292236328125], [Thu Dec 04 15:52:51 EST 2025, 47.41161346435547], [Thu Dec 04 15:53:09 EST 2025, 47.16603088378906], [Thu Dec 04 15:54:27 EST 2025, 45.966644287109375], [Thu Dec 04 15:54:33 EST 2025, 47.957862854003906], [Thu Dec 04 15:54:36 EST 2025, 45.921268463134766], [Thu Dec 04 15:54:48 EST 2025, 47.885108947753906], [Thu Dec 04 15:55:15 EST 2025, 46.322086334228516], [Thu Dec 04 15:55:24 EST 2025, 47.251853942871094], [Thu Dec 04 15:56:04 EST 2025, 45.09432601928711], [Thu Dec 04 15:56:07 EST 2025, 47.23249053955078], [Thu Dec 04 15:56:25 EST 2025, 45.86875534057617], [Thu Dec 04 15:56:34 EST 2025, 47.352333068847656], [Thu Dec 04 15:57:01 EST 2025, 46.46088790893555], [Thu Dec 04 15:57:10 EST 2025, 47.46621322631836], [Thu Dec 04 15:57:31 EST 2025, 46.279212951660156], [Thu Dec 04 15:57:34 EST 2025, 47.531532287597656], [Thu Dec 04 15:57:37 EST 2025, 45.556697845458984], [Thu Dec 04 15:57:40 EST 2025, 47.87958908081055], [Thu Dec 04 15:57:43 EST 2025, 46.11418151855469], [Thu Dec 04 15:57:55 EST 2025, 47.592315673828125], [Thu Dec 04 16:00:01 EST 2025, 46.093257904052734], [Thu Dec 04 16:00:10 EST 2025, 47.90593338012695], [Thu Dec 04 16:00:28 EST 2025, 46.700660705566406], [Thu Dec 04 16:02:38 EST 2025, 47.629051208496094], [Thu Dec 04 16:02:41 EST 2025, 45.794071197509766], [Thu Dec 04 16:02:50 EST 2025, 47.25967025756836], [Thu Dec 04 16:03:11 EST 2025, 46.328739166259766], [Thu Dec 04 16:03:14 EST 2025, 47.831172943115234], [Thu Dec 04 16:03:17 EST 2025, 46.3115234375], [Thu Dec 04 16:03:20 EST 2025, 48.050811767578125], [Thu Dec 04 16:03:23 EST 2025, 46.300479888916016], [Thu Dec 04 16:03:44 EST 2025, 46.82675552368164], [Thu Dec 04 16:05:12 EST 2025, 47.675697326660156], [Thu Dec 04 16:05:15 EST 2025, 45.6332893371582], [Thu Dec 04 16:05:18 EST 2025, 46.97443389892578], [Thu Dec 04 16:06:27 EST 2025, 45.93950271606445], [Thu Dec 04 16:06:30 EST 2025, 47.84481430053711], [Thu Dec 04 16:06:33 EST 2025, 45.939727783203125], [Thu Dec 04 16:06:36 EST 2025, 47.31392288208008], [Thu Dec 04 16:08:22 EST 2025, 45.269046783447266], [Thu Dec 04 16:08:28 EST 2025, 47.753597259521484], [Thu Dec 04 16:08:52 EST 2025, 46.437992095947266], [Thu Dec 04 16:09:40 EST 2025, 47.424137115478516], [Thu Dec 04 16:09:52 EST 2025, 46.816158294677734], [Thu Dec 04 16:13:23 EST 2025, 46.64979934692383], [Thu Dec 04 16:13:26 EST 2025, 48.0799446105957], [Thu Dec 04 16:13:29 EST 2025, 46.17212677001953], [Thu Dec 04 16:13:50 EST 2025, 47.31455612182617], [Thu Dec 04 16:14:56 EST 2025, 47.1671028137207], [Thu Dec 04 16:15:29 EST 2025, 46.222835540771484], [Thu Dec 04 16:16:41 EST 2025, 47.86396026611328], [Thu Dec 04 16:16:44 EST 2025, 45.7034912109375], [Thu Dec 04 16:16:59 EST 2025, 47.09933853149414], [Thu Dec 04 16:26:26 EST 2025, 46.577606201171875], [Thu Dec 04 16:26:29 EST 2025, 47.77180099487305], [Thu Dec 04 16:26:32 EST 2025, 45.40517044067383], [Thu Dec 04 16:26:35 EST 2025, 47.61018371582031], [Thu Dec 04 16:26:56 EST 2025, 46.42325210571289], [Thu Dec 04 16:29:20 EST 2025, 46.614803314208984], [Thu Dec 04 16:32:48 EST 2025, 47.46504211425781], [Thu Dec 04 16:32:57 EST 2025, 46.22206115722656], [Thu Dec 04 16:35:44 EST 2025, 47.3664665222168], [Thu Dec 04 16:36:29 EST 2025, 46.22618103027344], [Thu Dec 04 16:36:32 EST 2025, 47.50592803955078], [Thu Dec 04 16:36:53 EST 2025, 45.688419342041016], [Thu Dec 04 16:36:56 EST 2025, 47.64204406738281], [Thu Dec 04 16:37:26 EST 2025, 45.72358703613281], [Thu Dec 04 16:37:44 EST 2025, 47.2235107421875], [Thu Dec 04 16:38:05 EST 2025, 45.94649124145508], [Thu Dec 04 16:38:11 EST 2025, 47.40217208862305], [Thu Dec 04 16:38:17 EST 2025, 45.8856086730957], [Thu Dec 04 16:38:23 EST 2025, 47.58566665649414], [Thu Dec 04 16:38:50 EST 2025, 46.19305419921875], [Thu Dec 04 16:40:47 EST 2025, 47.31653594970703], [Thu Dec 04 16:41:17 EST 2025, 46.523075103759766], [Thu Dec 04 16:44:48 EST 2025, 48.29185485839844], [Thu Dec 04 16:44:51 EST 2025, 46.170074462890625], [Thu Dec 04 16:45:45 EST 2025, 47.7791633605957], [Thu Dec 04 16:46:03 EST 2025, 48.53673553466797], [Thu Dec 04 16:46:36 EST 2025, 52.18955993652344], [Thu Dec 04 17:12:34 EST 2025, 50.167301177978516], [Thu Dec 04 17:15:58 EST 2025, 49.69611358642578], [Thu Dec 04 17:55:38 EST 2025, 46.07004165649414], [Thu Dec 04 17:55:41 EST 2025, 47.843841552734375], [Thu Dec 04 17:55:45 EST 2025, 46.08115768432617], [Thu Dec 04 17:56:18 EST 2025, 47.3884391784668], [Thu Dec 04 17:56:30 EST 2025, 46.22011184692383], [Thu Dec 04 17:56:39 EST 2025, 47.09139633178711], [Thu Dec 04 17:57:39 EST 2025, 45.73651885986328], [Thu Dec 04 17:57:42 EST 2025, 47.85816192626953], [Thu Dec 04 17:57:48 EST 2025, 47.38394546508789], [Thu Dec 04 17:58:24 EST 2025, 47.87290573120117], [Thu Dec 04 17:58:27 EST 2025, 45.828678131103516], [Thu Dec 04 17:58:42 EST 2025, 47.269752502441406], [Thu Dec 04 17:59:00 EST 2025, 46.00988006591797], [Thu Dec 04 17:59:09 EST 2025, 47.957542419433594], [Thu Dec 04 17:59:12 EST 2025, 46.63042449951172], [Thu Dec 04 18:04:55 EST 2025, 47.3066520690918], [Thu Dec 04 18:05:31 EST 2025, 46.080562591552734], [Thu Dec 04 18:06:19 EST 2025, 47.438594818115234], [Thu Dec 04 18:06:49 EST 2025, 46.53171157836914], [Thu Dec 04 18:09:42 EST 2025, 47.90958023071289], [Thu Dec 04 18:09:45 EST 2025, 46.04317855834961], [Thu Dec 04 18:10:21 EST 2025, 48.08060836791992], [Thu Dec 04 18:10:24 EST 2025, 46.18787384033203], [Thu Dec 04 18:11:06 EST 2025, 47.42878341674805], [Thu Dec 04 18:11:24 EST 2025, 46.04720687866211], [Thu Dec 04 18:11:33 EST 2025, 47.332801818847656], [Thu Dec 04 18:12:39 EST 2025, 46.09174728393555], [Thu Dec 04 18:12:51 EST 2025, 47.3135871887207], [Thu Dec 04 18:14:28 EST 2025, 46.312904357910156], [Thu Dec 04 18:14:43 EST 2025, 47.261199951171875], [Thu Dec 04 18:15:34 EST 2025, 46.40986251831055], [Thu Dec 04 18:16:34 EST 2025, 47.27790451049805], [Thu Dec 04 18:17:40 EST 2025, 46.82395553588867], [Thu Dec 04 18:19:58 EST 2025, 45.477962493896484], [Thu Dec 04 18:20:01 EST 2025, 47.78178405761719], [Thu Dec 04 18:20:07 EST 2025, 47.25088882446289], [Thu Dec 04 18:24:30 EST 2025, 46.08639907836914], [Thu Dec 04 18:24:33 EST 2025, 48.0147705078125], [Thu Dec 04 18:24:51 EST 2025, 46.05486297607422], [Thu Dec 04 18:25:30 EST 2025, 47.26300811767578], [Thu Dec 04 18:26:34 EST 2025, 45.95487976074219], [Thu Dec 04 18:27:16 EST 2025, 47.380592346191406], [Thu Dec 04 18:30:31 EST 2025, 46.41165542602539], [Thu Dec 04 18:30:40 EST 2025, 47.82911682128906], [Thu Dec 04 18:30:49 EST 2025, 46.48750305175781], [Thu Dec 04 18:30:55 EST 2025, 47.01919174194336], [Thu Dec 04 18:32:38 EST 2025, 46.85212326049805], [Thu Dec 04 18:32:41 EST 2025, 45.15773391723633], [Thu Dec 04 18:32:56 EST 2025, 47.24235534667969], [Thu Dec 04 18:39:07 EST 2025, 46.255950927734375], [Thu Dec 04 18:39:10 EST 2025, 48.048095703125], [Thu Dec 04 18:39:13 EST 2025, 46.38821792602539], [Thu Dec 04 18:39:43 EST 2025, 47.47113800048828], [Thu Dec 04 18:41:22 EST 2025, 46.34101867675781], [Thu Dec 04 18:43:01 EST 2025, 47.407196044921875], [Thu Dec 04 18:43:14 EST 2025, 46.05341339111328], [Thu Dec 04 18:43:53 EST 2025, 47.569976806640625], [Thu Dec 04 18:44:26 EST 2025, 46.00157165527344], [Thu Dec 04 18:44:29 EST 2025, 47.74413299560547], [Thu Dec 04 18:44:53 EST 2025, 46.56635284423828], [Thu Dec 04 18:56:29 EST 2025, 47.31626892089844], [Thu Dec 04 18:56:47 EST 2025, 48.28163528442383], [Thu Dec 04 18:58:53 EST 2025, 47.48373794555664], [Thu Dec 04 18:59:05 EST 2025, 50.05424118041992], [Thu Dec 04 19:00:29 EST 2025, 50.70169448852539], [Thu Dec 04 19:00:51 EST 2025, 52.18955993652344], [Thu Dec 04 19:03:39 EST 2025, 52.18955993652344], [Thu Dec 04 19:14:48 EST 2025, 50.23786163330078], [Thu Dec 04 19:15:12 EST 2025, 49.03375244140625], [Thu Dec 04 19:31:01 EST 2025, 46.86906433105469], [Thu Dec 04 19:36:20 EST 2025, 45.961421966552734], [Thu Dec 04 19:36:24 EST 2025, 48.0367431640625], [Thu Dec 04 19:36:30 EST 2025, 46.71452331542969], [Thu Dec 04 19:37:09 EST 2025, 47.6085090637207], [Thu Dec 04 19:38:18 EST 2025, 46.54679870605469], [Thu Dec 04 19:44:10 EST 2025, 47.724205017089844], [Thu Dec 04 19:44:13 EST 2025, 46.12644958496094], [Thu Dec 04 19:44:19 EST 2025, 47.18888473510742], [Thu Dec 04 19:49:30 EST 2025, 45.95455551147461], [Thu Dec 04 19:49:36 EST 2025, 48.1844482421875], [Thu Dec 04 19:49:39 EST 2025, 46.155845642089844], [Thu Dec 04 19:50:15 EST 2025, 46.810394287109375], [Thu Dec 04 19:55:49 EST 2025, 46.99318313598633], [Thu Dec 04 20:09:22 EST 2025, 46.50411605834961], [Thu Dec 04 20:09:28 EST 2025, 46.74446105957031], [Thu Dec 04 20:11:05 EST 2025, 47.13508987426758], [Thu Dec 04 20:12:59 EST 2025, 46.459102630615234], [Thu Dec 04 20:13:23 EST 2025, 47.88423538208008], [Thu Dec 04 20:13:26 EST 2025, 46.42216110229492], [Thu Dec 04 20:14:26 EST 2025, 47.451820373535156], [Thu Dec 04 20:14:50 EST 2025, 46.363956451416016], [Thu Dec 04 20:16:22 EST 2025, 47.50119400024414], [Thu Dec 04 20:16:34 EST 2025, 46.35538864135742], [Thu Dec 04 20:16:58 EST 2025, 47.597862243652344], [Thu Dec 04 20:17:13 EST 2025, 46.60463333129883], [Thu Dec 04 20:18:37 EST 2025, 47.47768020629883], [Thu Dec 04 20:19:34 EST 2025, 46.44517517089844], [Thu Dec 04 20:22:38 EST 2025, 47.92182540893555], [Thu Dec 04 20:22:41 EST 2025, 46.21126937866211], [Thu Dec 04 20:23:05 EST 2025, 47.63313293457031], [Thu Dec 04 20:24:02 EST 2025, 46.28367614746094], [Thu Dec 04 20:24:23 EST 2025, 47.33415985107422], [Thu Dec 04 20:25:32 EST 2025, 46.445152282714844], [Thu Dec 04 20:26:02 EST 2025, 47.656673431396484], [Thu Dec 04 20:27:51 EST 2025, 46.56018829345703], [Thu Dec 04 20:29:57 EST 2025, 47.7087516784668], [Thu Dec 04 20:30:12 EST 2025, 46.50257873535156], [Thu Dec 04 20:32:25 EST 2025, 47.4967155456543], [Thu Dec 04 20:32:53 EST 2025, 46.35053634643555], [Thu Dec 04 20:34:17 EST 2025, 47.506439208984375], [Thu Dec 04 20:35:44 EST 2025, 46.08468246459961], [Thu Dec 04 20:35:53 EST 2025, 47.393707275390625], [Thu Dec 04 20:37:14 EST 2025, 46.553855895996094], [Thu Dec 04 20:39:18 EST 2025, 47.34282684326172], [Thu Dec 04 20:43:15 EST 2025, 46.38200378417969], [Thu Dec 04 20:43:18 EST 2025, 47.990333557128906], [Thu Dec 04 20:43:21 EST 2025, 46.1215705871582], [Thu Dec 04 20:43:24 EST 2025, 47.8768424987793], [Thu Dec 04 20:43:36 EST 2025, 46.545143127441406], [Thu Dec 04 20:44:16 EST 2025, 47.00385665893555], [Thu Dec 04 21:04:24 EST 2025, 47.68045425415039], [Thu Dec 04 21:04:42 EST 2025, 45.965576171875], [Thu Dec 04 21:04:45 EST 2025, 47.685428619384766], [Thu Dec 04 21:05:21 EST 2025, 46.71894073486328], [Thu Dec 04 21:11:47 EST 2025, 47.384521484375], [Thu Dec 04 21:12:02 EST 2025, 46.220916748046875], [Thu Dec 04 21:13:47 EST 2025, 47.512935638427734], [Thu Dec 04 21:14:08 EST 2025, 46.11501693725586], [Thu Dec 04 21:14:11 EST 2025, 47.60273742675781], [Thu Dec 04 21:15:54 EST 2025, 46.676124572753906], [Thu Dec 04 21:19:54 EST 2025, 47.5144157409668], [Thu Dec 04 21:20:36 EST 2025, 46.03337478637695], [Thu Dec 04 21:20:57 EST 2025, 47.54075241088867], [Thu Dec 04 21:21:06 EST 2025, 46.365150451660156], [Thu Dec 04 21:24:05 EST 2025, 47.18470001220703], [Thu Dec 04 21:25:35 EST 2025, 46.6080322265625], [Thu Dec 04 21:31:51 EST 2025, 47.42105484008789], [Thu Dec 04 21:33:22 EST 2025, 46.30924606323242], [Thu Dec 04 21:34:37 EST 2025, 47.45130920410156], [Thu Dec 04 21:34:40 EST 2025, 46.1158332824707], [Thu Dec 04 21:34:46 EST 2025, 46.74706268310547], [Thu Dec 04 21:35:46 EST 2025, 46.84524917602539], [Thu Dec 04 21:38:48 EST 2025, 47.481056213378906], [Thu Dec 04 21:38:51 EST 2025, 45.87385559082031], [Thu Dec 04 21:38:57 EST 2025, 47.23835372924805], [Thu Dec 04 21:41:09 EST 2025, 46.5411491394043], [Thu Dec 04 21:41:57 EST 2025, 47.49198532104492], [Thu Dec 04 21:42:33 EST 2025, 47.72723388671875], [Thu Dec 04 21:43:30 EST 2025, 52.18955993652344], [Thu Dec 04 21:56:23 EST 2025, 52.18955993652344]]
> 'Calculated Avg = 46.9925031222'
> 'Simple Average = 46.979143079'
> 'Difference = 0.0133600432245'

This isn’t a big deal obviously, but any insight would be appreciated.

Transistor · December 5, 2025, 4:29am

Hi, Philip. If you edit your post to format your return data as </> preformatted text (as you did with the script) rather than as a quotation, it will limit the post length and add a scroll bar to that section. As it is, it's 393 lines long on my portrait monitor. Thanks.

JVDM · December 5, 2025, 10:38am

This indeed is a very small difference, which makes me suspect it is a rounding error.

The Simple Average answer is one decimal shorter than your Calculated Avg, which makes me think calculations are done with one less decimal. I’m not sure how many records you have in this calculation, a few hundred small differences could just add up to 0,013.

Edit: I just noticed the following:

52.18955993652344 ← used in your data
46.9925031222 ← calculated average
46.979143079 ← Simple Average

I was doubtful that a few hundred of one-decimal differences could add up to 0.013, but it seems there are about 5 decimals missing, making me a bit more confident in this suspicion.

paul-griffith · December 5, 2025, 5:22pm

This is the value you get by averaging your input dataset, excluding the final row.

The historian does some complicated stuff I've never fully understood that includes or excludes certain values based on complicated internal logic. I don't think you've found a bug, although I'm not the person to explain all the nuances of this behavior

Live Code

Philip_Knowlton · December 5, 2025, 8:17pm

Oh, that’s very interesting! I wonder what the use-case/decision-point is that would cause it to not include a datapoint that you were explicitly trying to include…

Great find nonetheless, it makes me feel a little bit less crazy that the numbers were repeatable.

pturmel · December 5, 2025, 8:39pm

@paul-griffith, is the historian time-weighting the average? (Which I would expect if the intervals aren't exact....)

paul-griffith · December 5, 2025, 8:49pm

I think it's simpler than that - the last value in the dataset is 52.18955993652344 repeated twice, so I think it's the "seed" value being included (if the date range includes realtime now?)

Again, I'm not the person to explain all this

Philip_Knowlton · December 5, 2025, 8:59pm

@pturmel the SimpleAverage is supposed to be distinct from Average (time-weighted).

@paul-griffith I like playing “Stump The Developer”

I’ll try running it again tonight selecting a set window of time rather than using now() and we’ll see if we get a repeated value.

Philip_Knowlton · December 5, 2025, 9:19pm

@paul-griffith check this out:

I just ran the following, the only difference being that I’m selecting a static 1 hour of time:

path = ['[default]316/Hydro/Lane 1/DRIVE_OUTPUT_FREQ']
startDate = system.date.parse('2025-12-4 16:00:00')
endDate = system.date.parse('2025-12-4 17:00:00')
aggregationMode = 'SimpleAverage'
average = system.tag.queryTagHistory(paths=path, startDate=startDate, endDate=endDate, aggregationMode=aggregationMode, returnSize=1)
dataset = system.tag.queryTagHistory(paths=path, startDate=startDate, endDate=endDate)
data = system.dataset.toPyDataSet(dataset)

pyaverage = system.dataset.toPyDataSet(average)

data

sums = 0
count = 0
for item in data:
    sums += item[1]
    count += 1

calcAvg = sums/count
pyAvg    = pyaverage[0][1]
difference = abs(calcAvg - pyAvg)
'Calculated Avg = ' + str(calcAvg)
'Simple Average = ' + str(pyAvg)
'Difference = ' + str(difference)

It still returned a difference:

[[Thu Dec 04 16:00:01 EST 2025, 46.093257904052734], [Thu Dec 04 16:00:10 EST 2025, 47.90593338012695], [Thu Dec 04 16:00:28 EST 2025, 46.700660705566406], [Thu Dec 04 16:02:38 EST 2025, 47.629051208496094], [Thu Dec 04 16:02:41 EST 2025, 45.794071197509766], [Thu Dec 04 16:02:50 EST 2025, 47.25967025756836], [Thu Dec 04 16:03:11 EST 2025, 46.328739166259766], [Thu Dec 04 16:03:14 EST 2025, 47.831172943115234], [Thu Dec 04 16:03:17 EST 2025, 46.3115234375], [Thu Dec 04 16:03:20 EST 2025, 48.050811767578125], [Thu Dec 04 16:03:23 EST 2025, 46.300479888916016], [Thu Dec 04 16:03:44 EST 2025, 46.82675552368164], [Thu Dec 04 16:05:12 EST 2025, 47.675697326660156], [Thu Dec 04 16:05:15 EST 2025, 45.6332893371582], [Thu Dec 04 16:05:18 EST 2025, 46.97443389892578], [Thu Dec 04 16:06:27 EST 2025, 45.93950271606445], [Thu Dec 04 16:06:30 EST 2025, 47.84481430053711], [Thu Dec 04 16:06:33 EST 2025, 45.939727783203125], [Thu Dec 04 16:06:36 EST 2025, 47.31392288208008], [Thu Dec 04 16:08:22 EST 2025, 45.269046783447266], [Thu Dec 04 16:08:28 EST 2025, 47.753597259521484], [Thu Dec 04 16:08:52 EST 2025, 46.437992095947266], [Thu Dec 04 16:09:40 EST 2025, 47.424137115478516], [Thu Dec 04 16:09:52 EST 2025, 46.816158294677734], [Thu Dec 04 16:13:23 EST 2025, 46.64979934692383], [Thu Dec 04 16:13:26 EST 2025, 48.0799446105957], [Thu Dec 04 16:13:29 EST 2025, 46.17212677001953], [Thu Dec 04 16:13:50 EST 2025, 47.31455612182617], [Thu Dec 04 16:14:56 EST 2025, 47.1671028137207], [Thu Dec 04 16:15:29 EST 2025, 46.222835540771484], [Thu Dec 04 16:16:41 EST 2025, 47.86396026611328], [Thu Dec 04 16:16:44 EST 2025, 45.7034912109375], [Thu Dec 04 16:16:59 EST 2025, 47.09933853149414], [Thu Dec 04 16:26:26 EST 2025, 46.577606201171875], [Thu Dec 04 16:26:29 EST 2025, 47.77180099487305], [Thu Dec 04 16:26:32 EST 2025, 45.40517044067383], [Thu Dec 04 16:26:35 EST 2025, 47.61018371582031], [Thu Dec 04 16:26:56 EST 2025, 46.42325210571289], [Thu Dec 04 16:29:20 EST 2025, 46.614803314208984], [Thu Dec 04 16:32:48 EST 2025, 47.46504211425781], [Thu Dec 04 16:32:57 EST 2025, 46.22206115722656], [Thu Dec 04 16:35:44 EST 2025, 47.3664665222168], [Thu Dec 04 16:36:29 EST 2025, 46.22618103027344], [Thu Dec 04 16:36:32 EST 2025, 47.50592803955078], [Thu Dec 04 16:36:53 EST 2025, 45.688419342041016], [Thu Dec 04 16:36:56 EST 2025, 47.64204406738281], [Thu Dec 04 16:37:26 EST 2025, 45.72358703613281], [Thu Dec 04 16:37:44 EST 2025, 47.2235107421875], [Thu Dec 04 16:38:05 EST 2025, 45.94649124145508], [Thu Dec 04 16:38:11 EST 2025, 47.40217208862305], [Thu Dec 04 16:38:17 EST 2025, 45.8856086730957], [Thu Dec 04 16:38:23 EST 2025, 47.58566665649414], [Thu Dec 04 16:38:50 EST 2025, 46.19305419921875], [Thu Dec 04 16:40:47 EST 2025, 47.31653594970703], [Thu Dec 04 16:41:17 EST 2025, 46.523075103759766], [Thu Dec 04 16:44:48 EST 2025, 48.29185485839844], [Thu Dec 04 16:44:51 EST 2025, 46.170074462890625], [Thu Dec 04 16:45:45 EST 2025, 47.7791633605957], [Thu Dec 04 16:46:03 EST 2025, 48.53673553466797], [Thu Dec 04 16:46:36 EST 2025, 52.18955993652344], [Thu Dec 04 17:12:34 EST 2025, 50.167301177978516]]
'Calculated Avg = 47.0128024992'
'Simple Average = 46.9602275213'
'Difference = 0.052574977979'

Though what’s especially interesting is that it doesn’t seem to have repeated the last value in this dataset…

pturmel · December 5, 2025, 9:33pm

Paul is getting much better at dodging the nerd-sniping attempts.

robertm · December 5, 2025, 10:49pm

Out of curiosity, what's the value of you use Tag Query Calculation?

Philip_Knowlton · December 6, 2025, 12:47am

@robertm I’m helping a coworker build a simple application where he wanted the average from tag history. Long story short, I had some questions about how system.tag.queryTagHistory() worked with aggregations and why it returned certain values and set about learning through trials. That led me to this.

robertm · December 6, 2025, 12:02pm

Understood, but I was referring to a different method that I normally use: