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Round off error in the database?

  #21  
Old 09-10-2004, 06:54 AM
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Originally posted by Jason@Sep 9th 2004 @ 7:58 PM
Ah. Looks like that was the problem. I reset the variables when the script looped (recalculating all of the overall mileages) and it appears to have worked. Please double-check me on that.
I just did the Excel calculation for all cars in the database this morning. They all match exactly (except for those with override). Looking good!

Andy, thanks for being such a careful observer!
Well I fix nasty software problems for a living. Observing the problem, finding out what's wrong, and then convincing everybody involved that this is indeed what's wrong is what I do everyday

Andy

P.S. Oh, I was really busy at work yesterday. I was going to take a look at your code fragment last night but my home PC blow up. Took me all night to find out it's the video card and swap in an old card.
 
  #22  
Old 09-10-2004, 01:43 PM
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Hi Jason:

___I thought we had discussed the lmpg inaccuracy a few months ago with Rick Reese’s and my own tanks but I didn’t find the thread? In any case, my current spreadsheet lmpg now matches up with the database lmpg almost exactly. Wait until I post my next tank at which time my spreadsheet, my lmpg, and the database will finally match because it is going to be a good one

___Accwai, thanks for leaning on Jason for the accuracy fix. I always thought it was a significant digit problem and kept hammering on Jason to fix that to make the lmpg numbers match. Significant Database Updates, By Popular Request * tenth post + down …

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #23  
Old 09-10-2004, 09:54 PM
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Right, I remember that. I think the error was blamed on rounding, however. Unless I don't recall correctly, I assumed that whole-number distances and tenths-digit mileages was creating the abberance.

Ah, well. No reason to dwell on the past. It's fixed.
 
  #24  
Old 09-10-2004, 09:56 PM
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Looks like things aren't absolutely perfect after all... I see a "highway" percentage in the 90's while every tank's percentage was 0-33. I'll look into it. These are sort of useless variables, anyway
 
  #25  
Old 09-14-2004, 07:36 PM
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Eh, looks like I have a small bit to fix, still. I haven't yet updated the equations for the Month vs. Mileage graph. Remind me if I forget...
 
  #26  
Old 09-14-2004, 08:19 PM
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Originally posted by Jason@Sep 10th 2004 @ 11:56 PM
Looks like things aren't absolutely perfect after all... I see a "highway" percentage in the 90's while every tank's percentage was 0-33. I'll look into it. These are sort of useless variables, anyway
Not useless, its good for a quick scan of your competetors and what they are facing.
 
  #27  
Old 09-15-2004, 07:38 AM
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Haha, ok. Well, I'll look into it anyway.
 
  #28  
Old 09-16-2004, 01:42 PM
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My wholehearted "thank you" to both Andy and Jason for banging away at this. I appreciate your efforts, both of you!
 
  #29  
Old 09-18-2004, 12:04 PM
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Andy, for the life of me I cannot figure out why these values are wrong. If it works for mileage, why not the others, as well?

Code:
	if ($weight['mileage'] != 0) { $mileagedenominator = $mileagedenominator + $weight['distance']/$weight['mileage']; }
	if ($weight['temperature'] != 0) { $temperaturedenominator = $temperaturedenominator + $weight['distance']/$weight['temperature']; }
	if ($weight['time'] != 0) { $timedenominator = $timedenominator + $weight['distance']/$weight['time']; }
	if ($weight['highway'] != 0) { $highwaydenominator = $highwaydenominator + $weight['distance']/$weight['highway']; }
	if ($weight['traffic'] != 0) { $trafficdenominator = $trafficdenominator + $weight['distance']/$weight['traffic']; }
	
	$numerator= $numerator + $weight['distance'];
	
	if ($mileagedenominator != 0) { $mileage = $numerator / $mileagedenominator; }
	if ($temperaturedenominator != 0) { $temperature = round($numerator / $temperaturedenominator,0); }
	if ($timedenominator != 0) { $time = round($numerator / $timedenominator,0); }
	if ($highwaydenominator != 0) { $highway = $numerator / $highwaydenominator; }
	if ($trafficdenominator != 0) { $traffic = $numerator / $trafficdenominator; }
 
  #30  
Old 09-18-2004, 12:05 PM
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Side note: the main bar graph was running on numbers rounded to the tenth insteaded to the whole number. The drawing software rounded these values down. This has been fixed, resulting in a Prius II average of 50 instead of 49.

Side note #2: I am contemplating changing these values to medians instead of means in order to dissassociate "hypermilers."
 
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