# Modify part of a dataset
**URL:** https://discourse.paraview.org/t/modify-part-of-a-dataset/3060
**Category:** ParaView Support
**Created:** [November 27, 2019, 3:02pm UTC](https://discourse.paraview.org/t/modify-part-of-a-dataset/3060 "2019-11-27T15:02:40Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Tox](https://discourse.paraview.org/u/Tox)
#### Post date: [November 27, 2019, 3:02pm UTC](https://discourse.paraview.org/t/modify-part-of-a-dataset/3060/1 "2019-11-27T15:02:40Z")
Hello,
I have a (2d) dataset in which I would like to modify part of the data. What I can do is load the data, select the points that I want to modify (e.g. using the Select Points with Polygon option) and then use the ExtractSelection filter and apply a Calculator to the selection. However, I do not know how to put the modified region back into the original data set so that I can export the modified data set. Note that I am looking for a solution which is generic regarding the dataset (can also be unstructured polydata for instance) and the selection is also a generic selection of points in that dataset and does not need to be rectangular. Can I do this using the GUI in ParaView? Can I only do this in python? Can someone help me here?
Serge
Simple example: rectangular structured dataset of 4 columns (i) by 3 rows (j) with e.g. id values of:
1 2 3 4
5 6 7 8
9 10 11 12
Say I select i=1…2 with j=0…1 and I would like to set the selected point data to 0: result
1 0 0 4
5 0 0 8
9 10 11 12
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### Author:  [@wascott](https://discourse.paraview.org/u/wascott)
#### Post date: [November 27, 2019, 6:11pm UTC](https://discourse.paraview.org/t/modify-part-of-a-dataset/3060/2 "2019-11-27T18:11:38Z")
Lets see …
- Sources/ Mandlebrot. Apply.
- Surface (not sure if you need to do this, but it worked.)
- Select Cells with Polygon.
- Extract Selection. Apply.
- Turn visibility off for Extracted Selection, on for your source.
- Find Data. Invert Selection. Close Find Data.
- Extract Selection. Apply.
- Select both Extract Selections in the pipeline browser. Use the key.
- Group Datasets.