# Easy chart with tag drop multiple Axis

**URL:** <https://forum.inductiveautomation.com/t/easy-chart-with-tag-drop-multiple-axis/21306>\
**Category:** Ignition\
**Tags:** ignition79\
**Created:** [December 9, 2018, 3:41pm UTC](https://forum.inductiveautomation.com/t/easy-chart-with-tag-drop-multiple-axis/21306 "2018-12-09T15:41:04Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![bschroeder](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bschroeder/32/13260_2.png) [@bschroeder](https://forum.inductiveautomation.com/u/bschroeder)\
**Post date:** [December 9, 2018, 3:41pm UTC](https://forum.inductiveautomation.com/t/easy-chart-with-tag-drop-multiple-axis/21306/1 "2018-12-09T15:41:04Z")

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So… I’m sure there is an answer for this I just can’t seem to find it right now.

I’ve got an easy chart for a dynamic tag pick historian type page. When the operator drops the tag onto the chart there isn’t another axis added. I think I have to add the axis myself correct?

If I need to add the axis myself, how do I know if that tag has been removed from the chart so I can remove the axis as well?

Does anyone have any examples etc?

Thanks!

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [December 9, 2018, 7:15pm UTC](https://forum.inductiveautomation.com/t/easy-chart-with-tag-drop-multiple-axis/21306/2 "2018-12-09T19:15:25Z")

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You’ll want to override the onTagDropped() extension function of the easyChart to get the custom functionality you want. The default behaviour basically adds the appropriate details to the `tagPens` dataset, and I believe it uses whatever axis is present already (in the `axes` dataset). Your custom onTagDropped() function can add or update axes, manipulate the setting on the pen as you see fit, and even provide suitable functionality for the `pens` dataset (non-tag historian trends) where you have the relevant details available. You can leave unused entries in the `axes` dataset without harm – they won’t show if no pen is using them.

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<div class="post-metadata">

**Author:** ![bschroeder](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bschroeder/32/13260_2.png) [@bschroeder](https://forum.inductiveautomation.com/u/bschroeder)\
**Post date:** [December 9, 2018, 7:18pm UTC](https://forum.inductiveautomation.com/t/easy-chart-with-tag-drop-multiple-axis/21306/3 "2018-12-09T19:18:44Z")

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So when the X is clicked in the pens list to remove the pen from the chart the onTagDropped() extension is called?

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<div class="post-metadata">

**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [December 10, 2018, 3:53am UTC](https://forum.inductiveautomation.com/t/easy-chart-with-tag-drop-multiple-axis/21306/4 "2018-12-10T03:53:44Z")

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No, for that you’d use a propertyChange event that responds to propertyName equal to pens, tagPens, or calcPens. The configureChart extension function is also called on changes to the pens, but changing more will recurse.