# How to subtract time(t) data from time(0) data

**URL:** https://discourse.paraview.org/t/how-to-subtract-time-t-data-from-time-0-data/130
**Category:** ParaView Support
**Created:** [June 8, 2018, 12:43am UTC](https://discourse.paraview.org/t/how-to-subtract-time-t-data-from-time-0-data/130 "2018-06-08T00:43:12Z")
**Posts on this page:** 1
**Showing post:** 12

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### Author: ![gockolori](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/g/919ad9/32.png) [@gockolori](https://discourse.paraview.org/u/gockolori)
#### Post date: [November 19, 2019, 10:52am UTC](https://discourse.paraview.org/t/how-to-subtract-time-t-data-from-time-0-data/130/12 "2019-11-19T10:52:50Z")

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Heyo,  
I have to restart the discussion here.  
I am trying the above, but paraview keeps crashing when I apply the Python calculator.

One difference I have, is that I am dealing with CellData. But that shouldn’t make a difference, right?

Another way I tried also did **not** work:  
Importing group of data (this i the time-series of cellData)  
importing the data(t=0) and use the calculator to rename the “arr” as “base”/ or use the ForceTimeFilter  
then use append datasets to combine data (of all time steps) with the calculated “base”  
then use the “normal” calculator filter to subtract arr - base --\> then my timesteps are lost, an the operation is only done for the first time step, which results in diffences of e-38, which I guess is the computational precision limit

Any suggestions?  
I am using PV 5.4.1 on Ubuntu 18.04

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