How to subtract a current value from loop iteration to value from previous loop iteration

[achimost]

Hi,

I have a series of value getting from an experiment. It is located in the white loop section. 

For example: 1   ;   3   ;  6;    9. (the last value is 9)

After running an analysis, the value (put in the loop) update to 1; 3; 6;9; 15 (the update value is 15)

Then for other run, the value (put in the loop) update to 1; 3; 6;9; 15; 25 (the update value is 25)

 I want to do a subtraction between 2 last value from the loop iteration. for this case 15- 9 = 6 and then 25 -15 = 10.

Could you please tell me the way to solve this problem?

Thanks

[Bob_Schor]

Open LabVIEW, go to Help, LabVIEW Help, click the Index Tab, type "Shift Registers", and read the Help Text.  Then write a little VI and try it out.

If this is brand new to you, for goodness sake, find some basic LabVIEW Tutorial Material and spend the time!

Bob Schor

[apok]

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 SR would be a start 

[altenbach]

For a change in scenery, you could also use a feedback node. 😄

[altenbach]

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@apok wrote:
SR would be a start 

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Status report? Success rate? Solar radiation? Senate resolution? Service request? Special relativity? ...

[cdaug · Accepted solution]

Hi Achimost, this is Chris with National Instruments Applications Engineering. I know it has already been mentioned, but I wanted to provide some resources with basic information on Shift Registers. These are how we pass data between different loop iterations in LabVIEW. I would encourage looking into Stacked Shift Registers in the first link.

Passing Data Between Loop Iterations in LabVIEW

http://www.ni.com/getting-started/labview-basics/shift-registers

Shift Registers: Passing Values between Loop Iterations

http://zone.ni.com/reference/en-XX/help/371361J-01/lvconcepts/shift_registers_concepts/

I also had some extra time and created an example illustrating the behavior you mentioned. Reading up on the above articles will help explain what you're seeing a lot better!