# Display difference of two history tag on easy chart

**URL:** <https://forum.inductiveautomation.com/t/display-difference-of-two-history-tag-on-easy-chart/27707>\
**Category:** Ignition\
**Created:** [August 23, 2019, 11:19am UTC](https://forum.inductiveautomation.com/t/display-difference-of-two-history-tag-on-easy-chart/27707 "2019-08-23T11:19:31Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![nader.chinichian](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nader.chinichian/32/9261_2.png) [@nader.chinichian](https://forum.inductiveautomation.com/u/nader.chinichian)\
**Post date:** [August 23, 2019, 11:19am UTC](https://forum.inductiveautomation.com/t/display-difference-of-two-history-tag-on-easy-chart/27707/1 "2019-08-23T11:19:31Z")

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Hi  
For easy chart pen is it possible to display difference of two history tag?

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**Author:** ![grietveld](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/grietveld/32/6984_2.png) [@grietveld](https://forum.inductiveautomation.com/u/grietveld)\
**Post date:** [August 23, 2019, 11:48am UTC](https://forum.inductiveautomation.com/t/display-difference-of-two-history-tag-on-easy-chart/27707/2 "2019-08-23T11:48:15Z")

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I don’t have any history tags to test my theory on, but you should be able to use a calculated pen.

Function Difference, and then set your pens to be the two tags you are wanting to calculate the difference of.

[https://docs.inductiveautomation.com/display/DOC79/Easy+Chart+-+Calculated+Pens](https://docs.inductiveautomation.com/display/DOC79/Easy+Chart+-+Calculated+Pens)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/2X/2/2c8fbc7d2da953adb489114b474658f6d5852731.png)

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<div class="post-metadata">

**Author:** ![nader.chinichian](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nader.chinichian/32/9261_2.png) [@nader.chinichian](https://forum.inductiveautomation.com/u/nader.chinichian)\
**Post date:** [August 24, 2019, 5:53am UTC](https://forum.inductiveautomation.com/t/display-difference-of-two-history-tag-on-easy-chart/27707/3 "2019-08-24T05:53:04Z")

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Hi  
Thanks