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PIAF analyses - Compute average of moving range

Question asked by simon76 on Apr 4, 2018
Latest reply on Apr 9, 2018 by simon76

Hi everyone,


I started to work on PIAF 2-3 weeks ago and I would like some help for an issue that I have. My objective is to construct an individual measurements control chart with PIAF analyses (expression).

The measures are vibrations and come from PI system. Below, a sample of my values:

DateValue (mm/s)MR
21-juil-17 00:00:002,202375345
21-juil-17 04:00:002,1106269160.09174
21-juil-17 08:00:002,2289304860.11830
21-juil-17 12:00:001,9358207790.29310
21-juil-17 16:00:002,2020279160.26620
21-juil-17 20:00:002,3096844070.10765
22-juil-17 00:00:002,4363989570.12671


So, I need to compute UCL (UCL = /x + 3 * /MR/1.128 ; LCL = UCL = /x - 3 * /MR/1.128).

/x is average of column value. (computed with TagAvg() like the screenshot below).


/MR is the average of the column MR. MR = |value i – value i-1|

My problem is to compute /MR with PIAF. I don't know how could I do this because when we use an expression we can't have the same attribute in input and in output.

Maybe you have an idea to do that (I hope).


Thank you for your time,