# Add the cell center coordinates to the cell data

**URL:** https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560
**Category:** ParaView Support
**Created:** [September 12, 2018, 7:09am UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560 "2018-09-12T07:09:02Z")
**Posts on this page:** 9
**Page:** 1

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### Author: ![pcrepier](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/p/f4b2a3/32.png) [@pcrepier](https://discourse.paraview.org/u/pcrepier)
#### Post date: [September 12, 2018, 7:09am UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/1 "2018-09-12T07:09:03Z")

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Hi everyone,

The solver I use being cell centered, I try more and more to work on the cell data to avoid having the use the cell data to point data filter. The only reason I have to interpolate to the points is to re-calculate moments because I do not have access to the cell centers in a cell data array.Using the cell centers filter does calculate this, but it outputs points … which because unhandy to use the integrate variables filter later on.

So, does anyone knows a trick to get append the cell centers to the cell data, but also keeping my unstructured grid ?

Thanks in advance.

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### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [September 12, 2018, 1:13pm UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/2 "2018-09-12T13:13:47Z")

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It’s a bit wonky, but it is possible to append the coordinates of the cell centers to the mesh. The following steps should work.

1. Add the `Cell Centers` filter. Turn on the `Vertex Cells` property. `Apply`.
2. Add the calculator filter. Set the `Result Array Name` to “Center” and the expression to compute to “coords”. `Apply`.
3. Add the `Point Data to Cell Data` filter. `Apply`.
4. In the pipeline browser, select both your original data set and the `Point Data to Cell Data` filter you just created. Add the `Append Attributes` filter. `Apply`.

That should do it.

For a bit more details, here is what each step is doing.

Step 1 is create a vertex cell (cell containing only one point) at the center of each cell in your original data set.

Step 2 is moving the point coordinates of each point to field data. Because of limitations of the calculator, it gets attached to points instead of cells.

Step 3 moves the field from points to cells. Because each cell only has one point, the values do not change.

Step 4 copies this cell field back to your original dataset.

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### Author: ![pcrepier](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/p/f4b2a3/32.png) [@pcrepier](https://discourse.paraview.org/u/pcrepier)
#### Post date: [September 13, 2018, 11:16am UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/3 "2018-09-13T11:16:39Z")

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Thanks for the hint. It’s doing the trick!

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### Author: ![banesullivan](https://discourse.paraview.org/user_avatar/discourse.paraview.org/banesullivan/32/11714_2.png) [@banesullivan](https://discourse.paraview.org/u/banesullivan)
#### Post date: [September 13, 2018, 11:54pm UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/4 "2018-09-13T23:54:36Z")

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You could also accomplish this with a custom filter plugin! I had a similar problem and made a filter you could load into PV 5.6.0+. Check it out:

```auto
"""
A snippet for add cell center coordinates to the CellData of an input dataset.

Created by Bane Sullivan <banesullivan@gmail.com> for the PVGeo project <http://pvgeo.org>
"""
from paraview.util.vtkAlgorithm import *
from vtk.util.vtkAlgorithm import VTKPythonAlgorithmBase
import numpy as np
import vtk
from vtk.util import numpy_support as nps
from vtk.numpy_interface import dataset_adapter as dsa

MENU_CAT = 'Custom Filters'

# Extract Cell Centers
@smproxy.filter(name='AppendCellCenters', label='Append Cell Centers')
@smhint.xml('''<ShowInMenu category="%s"/>
    <RepresentationType view="RenderView" type="Surface" />''' % MENU_CAT)
@smproperty.input(name="Input", port_index=0)
@smdomain.datatype(dataTypes=["vtkDataSet"], composite_data_supported=True)
class AppendCellCenters(VTKPythonAlgorithmBase):
    """A filter to extract the cell centers of a data object and append those
    coordinates as a 3-component double array on the Cell Data.

    Created by Bane Sullivan <banesullivan@gmail.com> for the PVGeo project <http://pvgeo.org>
    """
    def __init__ (self, **kwargs):
        VTKPythonAlgorithmBase. __init__ (self, nInputPorts=1, nOutputPorts=1, inputType='vtkDataSet')

    # THIS IS CRUCIAL to preserve data type through filter
    def RequestDataObject(self, request, inInfo, outInfo):
        """This method lets the pipeline know that the algorithm will dynamically decide
        the output data type based in the input data type.
        """
        self.OutputType = self.GetInputData(inInfo, 0, 0).GetClassName()
        self.FillOutputPortInformation(0, outInfo.GetInformationObject(0))
        return 1

    def RequestData(self, request, inInfoVec, outInfoVec):
        pdi = self.GetInputData(inInfoVec, 0, 0)
        pdo = self.GetOutputData(outInfoVec, 0)
        # Find cell centers
        filt = vtk.vtkCellCenters()
        filt.SetInputDataObject(pdi)
        filt.Update()
        # I use the dataset adapter/numpy interface because its easy
        centers = dsa.WrapDataObject(filt.GetOutput()).Points
        centers = nps.numpy_to_vtk(centers)
        centers.SetName('Cell Centers')
        # Copy input data and add cell centers as tuple array
        pdo.DeepCopy(pdi)
        pdo.GetCellData().AddArray(centers)
        return 1

```

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### Author: ![kayarre](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kayarre/32/1994_2.png) [@kayarre](https://discourse.paraview.org/u/kayarre)
#### Post date: [January 4, 2022, 4:27pm UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/5 "2022-01-04T16:27:24Z")

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@banesullivan this should work in the latest releases as well? 5.9+?

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### Author: ![Andrei](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/a/9fc29f/32.png) [@Andrei](https://discourse.paraview.org/u/Andrei)
#### Post date: [July 20, 2022, 9:13am UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/6 "2022-07-20T09:13:41Z")

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It may be useful to add an additional step 3a with a Pass Arrays filter that excludes all data arrays except the newly created Centers. This will avoid duplication of data in the output from Append Attributes filter.

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### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [August 31, 2022, 9:59pm UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/7 "2022-08-31T21:59:49Z")

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I ended up revisiting this topic while answering a different question. I found my original solution is behaving a little wonky. @banesullivan’s plugin script works great, but fails on multiblock data sets. I found a slightly simpler solution.

1. Add the `Calculator` filter. Set the `Attribute Type` to `Point Data`. Set the `Result Array name` to `Cell Center`. Set the expression to `coords`. `Apply`.
2. Add the `Point Data to Cell Data` filter. Uncheck `Process All Arrays`. Uncheck all point arrays except `Cell Center`. Check `Pass Point Data`. `Apply`.

The result should be one more cell field with the cell centers. This should work with any data set whether multi-block or single data set. To make this even easier, here is a custom filter that just adds the `Cell Center` array as a single filter.

[AppendCellCenters.cpd](https://discourse.paraview.org/uploads/short-url/z8SQTtWUNP42lSsUnvHm0Ev7Tj8.cpd) (5.2 KB)

To load this, go to `Tools` → `Manage Custom Filters...`. Then click the `Import` button to load this file.

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<div class="post-metadata">

### Author: ![pcrepier](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/p/f4b2a3/32.png) [@pcrepier](https://discourse.paraview.org/u/pcrepier)
#### Post date: [September 1, 2022, 6:17am UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/8 "2022-09-01T06:17:20Z")

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I think there is a much easier solution to that problem now: use the “Append Location Attributes” filter since it gives access to the cell centers directly and avoid all weird solution.

I used to be affected by some bug however: [https://gitlab.kitware.com/paraview/paraview/-/issues/20890](https://gitlab.kitware.com/paraview/paraview/-/issues/20890)

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### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [September 1, 2022, 12:47pm UTC](https://discourse.paraview.org/t/add-the-cell-center-coordinates-to-the-cell-data/560/9 "2022-09-01T12:47:07Z")

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Awesome. I missed that filter. That is much better.