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       VEH-44: Per Garage CPM Calculations

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Issue Type: Improvement 
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Issue Information
====================

Priority: Minor					Status:      Closed
Resolution:  Won't Fix (2019-09-09 16:22:13)
Project: VehMan (VEH)


Reported By: btasker					
Assigned To: btasker

Components: 
	- Charts 
	- Statistics 


Targeted for fix in version: 
	- 1.5


Time Estimate: 0 minutes
Time Logged:   0 minutes


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Issue Description
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Generate cost per mile on a per garage basis - allowing for  comparison of fuel economy
between different garages.

Needs  to be carefully implemented though as the metric that needs to be used is the
distance between the current and the next  fill;

|Garage|Litres|Mileage|PPL|
|Tesco|12|1|£1|
|Shell|10|11|£1.50|
|Texaco|5|21|£1.25|

From the table above we could calculate

|Garage|Economy|CPM|
|Tesco|1 mile per litre|£1|
|Shell|2 miles per litre|75p|
|Texaco| - | - |

i.e. after filling up at Tesco's, a journey of 10 miles required us to put another 10
litres in the tank.  The fuel we bought at Tesco's was £1 a litre (I wish) therefore 

_(10 miles / 10 litres) * £1 = £1 per mile_


May be tricky to generate monthly per-garage CPM stats as it's unlikely that all recorded
garages will be used each month - an overall stat is probably the better move.


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Activity
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2013-11-17 06:12:00              btasker
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Might be possible to generate the base statistics at a monthly level though, would make
for easier recalculation of the overall statistic.

So in the stats table, we might add

|Year|Month|StatType|Value|Modifier|Description|
|2013|11|GarageFuelBurnt|10|Tesco|In the example above, we had to replace 10 litres of
Tesco petrol|
|2013|11|GarageTotalSpend|12|Tesco|In the example above, we bought 12 litres of petrol at
£1 from Tesco|
|2013|11|GarageTotalMileage|10|Tesco|In the example above, we travelled 10 miles burning
Tesco petrol|

That final statistic will be the most complex to generate, in the sense that we don't want
to resort to consistently querying for the next record - it'll put quite a load on the
database if we're not careful.


	
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2013-11-17 06:14:29              btasker
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One thing we also need to watch out for (and there's no real way to adjust for it). In the
example above, we purchased 12 litres from Tesco, travelled 10 miles and then purchased 10
litres from Shell.

From a stats point of view we then travelled another 10 miles on Shell petrol, before
replacing 5 litres of it.

In reality though, at that point we're travelling with a blend of Shell/Tesco petrol (we
know from the stats that the tank holds at least 12 litres). This will almost certainly
affect fuel economy, but there's no easy way to quantify it from a stats generation point
of view.

The best thing we can do is probably to add an FAQ somewhere which explains why you might
see a spike/dip in the chart just after changing garages.
	
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2019-09-09 16:22:13              btasker
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Bulk Close.

Realistically, this project's not going to see any further development (other than
possibly some bug fixes for anything new that's found).

Closing any outstanding issues as Won't Fix
	
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2019-09-09 16:22:13              
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btasker changed status from 'Open' to 'Closed'
	
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2019-09-09 16:22:13              
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btasker added 'Won't Fix' to resolution