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Cannot override output timestamp if any output is used as an input within an analysis

Question asked by PatrickCrummie on Jan 19, 2017
Latest reply on Jan 20, 2017 by Roger Palmen

I am trying to calculate a cumulative flow. I kick of the calculation at 12:05 after other daily totals have been calculated. I read the cumulative total from the previous day:

 

  CumQgYesterday ::      TagVal('Cum_Qg', 't-12')

and add the new daily total:

  CumQgToday ::         cumQgYesterday + 'Qg'

I then output the second result back to Cum_Qg

 

The calculation works fine when I look at the Preview Results. However if I attempt to adjust the timestamp using the Advanced Options, I get the message 'Cannot override output timestamp if any output is used as an input within an analysis'. I can see that there could be potential problems overwriting the input that you are reading in an analysis. However, surely what I am doing here is safe as i am reading yesterdays value, and creating a new point. Is there something about the way analyses work that would make this risky? Does anybody know the reason behind this behaviour? Is there a way to override this and adjust the output timestamp?

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