Calculating MTBF

Mon, 18 Aug 2014 13:00:44 GMT

Hi guys,

I'm new to Qlikview, and I'm having some problems with calculating a so called MTBF (Mean time between failures).

My input data is as follows:

Loc ID	Maintenance type	Mileage	Date
1	CM	10000	1-1-2010
1	PM	20000	1-5-2010
1	CM	30000	1-1-2011
1	PM	40000	1-10-2012
2	CM	10000	1-1-2010
2	CM	60000	1-1-2012
2	PM	80000	1-5-2012
3	CM	10000	1-1-2010
3	PM	30000	1-5-2010
3	CM	125000	13-12-2013

Now, the MTBF is determined by taking the average of either the mileages or the days passed between 2 CM maintenances. So the PM have to be left out of the equation. For example, LOC 1 had a CM at 10000 mile at date 1-1-2010. Its next CM was done at a mileage of 30000 at 1-1-2011. This means it has an MTBF of 20000 miles or 365 days. Furthermore, the latest CM date has to be displayed for each loc. Now I've been trying to do so with the Date(Max("Date") expression, but I'm unsure on how to calculate the amount of days between 2 CM's, let alone averaging all those days into a single number (the MTBF).

Hopefully someone can be of assistance here? Just point me in the right direction!

With regards,

Stijn

Re: Calculating MTBF

lft — Mon, 18 Aug 2014 13:23:13 GMT

Hi,

would that work ?

Loic

Re: Calculating MTBF

martynlloyd — Mon, 18 Aug 2014 13:33:18 GMT

If you do this in the script, it should be a lot easier to create your chart.

To calculate days look at INTERVAL and INTERVAL#

Interval(Date1 - Date2, 'D') as Days

To calculate between current row and previous , look at PEEK .

regards,

Marty.

Re: Calculating MTBF

Mon, 18 Aug 2014 15:04:27 GMT

With some minor tweaks your solution works perfectly! Thank you for your swift response.

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Calculating MTBF

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