How to change the index of the first point for plotting

ParaView Support
1

Hello,

I have the following set of vertex cells as shown in the screenshot below:

image
image1920×762 75 KB

These vertex cells are ordered counter-clockwise as indicated (notice the cells with index 0, 1, … 13, … etc).

When I use the “Plot Data” Filter and checking the option “Use Index for X Axis” (as shown below):

image
image1920×735 60.9 KB

I want to shift the index of the points: So for example: I want the point with index 13 (shown in the first screenshot above) to be the point with index 0, Index 14 to be index 1, and so on. As a result, the plot will be shifted horizontally.

How to achieve that in ParaView?

I appreciate your help.

Thank you

2

you need to compute this shifted index. I think the simplest way would probably be by using a programmable filter to compute it.

3

How?

4

https://docs.paraview.org/en/latest/ReferenceManual/pythonProgrammableFilter.html

5

I tried with this:

data = inputs[0]

# Get the number of points in the dataset
numPoints = data.GetNumberOfPoints()

# Create a new vtkPoints container for the rotated order
newPoints = vtk.vtkPoints()
newPoints.SetNumberOfPoints(numPoints)

offset = 13
for i in range(numPoints):
    # Compute the original index for the new index i
    originalIndex = (i + offset) % numPoints
    pt = data.GetPoint(originalIndex)
    newPoints.SetPoint(i, pt)

# Copy the input to the output so that other data (like cell data) is preserved
output.ShallowCopy(data)

# Replace the points in the output with the newly ordered points
output.SetPoints(newPoints)

But I get this error:

Traceback (most recent call last):
  File "<string>", line 22, in <module>
  File "<string>", line 15, in RequestData
  File "C:\Program Files\ParaView 5.13.2\bin\Lib\site-packages\vtkmodules\numpy_interface\dataset_adapter.py", line 128, in __getattr__
    return getattr(self.VTKObject, name)
AttributeError: 'vtkmodules.vtkCommonDataModel.vtkMultiBlockDataSet' object has no attribute 'GetPoint'