# subtracting line data from a plane

**URL:** https://discourse.paraview.org/t/subtracting-line-data-from-a-plane/8468
**Category:** ParaView Support
**Created:** [November 23, 2021, 4:00pm UTC](https://discourse.paraview.org/t/subtracting-line-data-from-a-plane/8468 "2021-11-23T16:00:36Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![kbshariff](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/k/0ea827/32.png) [@kbshariff](https://discourse.paraview.org/u/kbshariff)
#### Post date: [November 23, 2021, 4:00pm UTC](https://discourse.paraview.org/t/subtracting-line-data-from-a-plane/8468/1 "2021-11-23T16:00:36Z")

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Hello,  
I have a channel flow, I would like to subtract the turbulent intensity at the side wall in the whole domain.

How can I do that with paraview calculator?

I want to the the contour plot of this value

I = Iw^2 - Io^2;

Iw is the total turbulence

I would like to subtract the turbulence intensity  
Io is the turbulence at the lateral surface;

I attached figure for clarity

 ![lat3](https://discourse.paraview.org/uploads/default/original/2X/6/63369bb2f594a167e1adaa74d03618d28215ff35.jpeg)  
 ![lat](https://discourse.paraview.org/uploads/default/original/2X/f/fd8906b3abd5ece5f8ae89c6616def037e20050e.png)

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### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 24, 2021, 10:10am UTC](https://discourse.paraview.org/t/subtracting-line-data-from-a-plane/8468/2 "2021-11-24T10:10:10Z")

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Probably can be done with the python calculator, if not with a ProgrammableFilter

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### Author: ![kbshariff](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/k/0ea827/32.png) [@kbshariff](https://discourse.paraview.org/u/kbshariff)
#### Post date: [November 24, 2021, 12:28pm UTC](https://discourse.paraview.org/t/subtracting-line-data-from-a-plane/8468/3 "2021-11-24T12:28:01Z")

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Thank you Mathieu,

How can I extract the turbulence data along the lateral line (Iamb) in python calculator?

Sorry am a newbie

Thanks