# Accessing Tag History for Further Manipulation before Displaying

**URL:** <https://forum.inductiveautomation.com/t/accessing-tag-history-for-further-manipulation-before-displaying/45793>\
**Category:** Ignition\
**Created:** [April 20, 2021, 6:24am UTC](https://forum.inductiveautomation.com/t/accessing-tag-history-for-further-manipulation-before-displaying/45793 "2021-04-20T06:24:13Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![shanaka](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@shanaka](https://forum.inductiveautomation.com/u/shanaka)\
**Post date:** [April 20, 2021, 6:24am UTC](https://forum.inductiveautomation.com/t/accessing-tag-history-for-further-manipulation-before-displaying/45793/1 "2021-04-20T06:24:13Z")

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Hi All,

I’m pretty new to Ignition. I have a requirement to access tag history where we store voltage values, calculate averages and show them as a chart. I know you can drag and drop historical tags onto a chart control and necessary bindings are created automatically. However, my requirement is NOT to display historical data as it is. I need to calculate averages and show them as a chart. The problem encountered is that I don’t know how to access history data within an expression of a query so that I can manipulate them. Am I doing it wrong? Any advice, directions would be highly appreciated.

P.S. Ignition version is 7.9

Best regards,  
Shanaka

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**Author:** ![zacht](https://avatars.discourse-cdn.com/v4/letter/z/ea5d25/32.png) [@zacht](https://forum.inductiveautomation.com/u/zacht)\
**Post date:** [April 20, 2021, 2:36pm UTC](https://forum.inductiveautomation.com/t/accessing-tag-history-for-further-manipulation-before-displaying/45793/2 "2021-04-20T14:36:00Z")

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The tag historian has an aggregation mode of ‘Average’ and ‘Time Weighted Average’ (or something like those two). There’s a good chance you can use that to get what you need without having to do the calculations yourself.

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**Author:** ![shanaka](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@shanaka](https://forum.inductiveautomation.com/u/shanaka)\
**Post date:** [April 21, 2021, 10:25am UTC](https://forum.inductiveautomation.com/t/accessing-tag-history-for-further-manipulation-before-displaying/45793/4 "2021-04-21T10:25:34Z")

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Thanks a lot for the reply. Yes, this might help. I’ll have a look.

Best regards.