# Add calculated pens (sum of two pens, difference of two pens, etc) to Perspective Power Chart

**URL:** <https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858>\
**Category:** Ignition\
**Tags:** ignition81, perspective\
**Created:** [May 17, 2023, 6:53pm UTC](https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858 "2023-05-17T18:53:48Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Kevin\_Ar](https://avatars.discourse-cdn.com/v4/letter/k/b4bc9f/32.png) [@Kevin\_Ar](https://forum.inductiveautomation.com/u/Kevin_Ar)\
**Post date:** [May 17, 2023, 6:53pm UTC](https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858/1 "2023-05-17T18:53:48Z")

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I have two tags with history configured, TagA and TagB. I have a Power Chart in Perspective that I have added both tags to. Is there a way to configure a tag on the Power Chart TagC = TagA+TagB without configuring TagC as an expression tag with its own history?

I'm looking to have similar functionality to the Calculated Pens available in the Easy Chart component in Vision

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**Author:** ![mazeyrat](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mazeyrat/32/10955_2.png) [@mazeyrat](https://forum.inductiveautomation.com/u/mazeyrat)\
**Post date:** [May 17, 2023, 8:19pm UTC](https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858/2 "2023-05-17T20:19:27Z")

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+1 for this feature, and another similar need would be a **shifted tag** : in order to compare for the same value a week and the previous week on the same chart

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**Author:** ![brian.mcenulty](https://avatars.discourse-cdn.com/v4/letter/b/b77776/32.png) [@brian.mcenulty](https://forum.inductiveautomation.com/u/brian.mcenulty)\
**Post date:** [May 24, 2023, 6:52pm UTC](https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858/3 "2023-05-24T18:52:04Z")

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+1 here as well. On the Vision Easy Chart we often use the calculated pens feature and there doesn't seem to be a way to even roll your own with the Perspective Power Chart as the underlying datasets for each pen are not exposed.

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**Author:** ![Spencer\_Odom](https://avatars.discourse-cdn.com/v4/letter/s/b2d939/32.png) [@Spencer\_Odom](https://forum.inductiveautomation.com/u/Spencer_Odom)\
**Post date:** [August 12, 2024, 9:56pm UTC](https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858/4 "2024-08-12T21:56:22Z")

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Any updates on this?

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**Author:** ![Eugene49](https://avatars.discourse-cdn.com/v4/letter/e/c6cbf5/32.png) [@Eugene49](https://forum.inductiveautomation.com/u/Eugene49)\
**Post date:** [April 1, 2025, 1:43am UTC](https://forum.inductiveautomation.com/t/add-calculated-pens-sum-of-two-pens-difference-of-two-pens-etc-to-perspective-power-chart/73858/5 "2025-04-01T01:43:38Z")

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+1.  
I have multiple tags on power chart.  
I have a need to divide each tag by a number.

What is the long version to do this (without using expression tag)? Is it even possible for power charts?

Edit:  
Would this work?  
I would bind a property to a direct tag,  
on property change, I would do computation on the fly and write to a tag..  
(I need to do computation on the fly, so I can't create expression initially)