easyChart - compare the same tag with a time shift

We need to compare with easychart the history of the same tag value with a time shift. For example the temperature chart for week N and week N-1 on the same chart.
A calculed pen History with operation like plus/minus delta time would be cool.

Is there a way to achieve this feature with Ignition 7.9.X or 8.0 ?

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We did this using a second chart over-layed on the first with a transparent background.

Thanks for this workaround in the meantime. A new calculated pen would be more suitable for this need.

Hmmm. Sounds like a feature I could add to NoteChart. The key is to adjust the query parameters for the pen so there’s data to shift into the target time span.


Aside from an overlay, a view in the database would give you that, since easychart can also access views.

SELECT t_stamp, value as 'now', null as 'lastweek'
SELECT DATEADD(week,1,t_stamp), null as 'now', value as 'lastweek' )

I used views often for easychart, since there’s no way to directly manipulate data.