# How to compute plot values from tag historian

**URL:** <https://forum.inductiveautomation.com/t/how-to-compute-plot-values-from-tag-historian/33504>\
**Category:** Ignition\
**Created:** [March 29, 2020, 2:01am UTC](https://forum.inductiveautomation.com/t/how-to-compute-plot-values-from-tag-historian/33504 "2020-03-29T02:01:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![zane.cardwell](https://avatars.discourse-cdn.com/v4/letter/z/77aa72/32.png) [@zane.cardwell](https://forum.inductiveautomation.com/u/zane.cardwell)\
**Post date:** [March 29, 2020, 2:01am UTC](https://forum.inductiveautomation.com/t/how-to-compute-plot-values-from-tag-historian/33504/1 "2020-03-29T02:01:07Z")

</div>

For example i have a tag that ranges between 0 and 10. For some reason i want to divide this by two so it only goes to 5. i want to do this without imply hacking the Y-axis.

abother example, i want to create a ribbon chart, where anything above 4 shows as 1, and everything else as zero. again withoutdoing dodgy stuff to Y axit