# Vector operations in Python Calculator
**URL:** https://discourse.paraview.org/t/vector-operations-in-python-calculator/17217
**Category:** ParaView Support
**Created:** [September 27, 2025, 3:25pm UTC](https://discourse.paraview.org/t/vector-operations-in-python-calculator/17217 "2025-09-27T15:25:29Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Captain\_Convergence](https://discourse.paraview.org/u/Captain_Convergence)
#### Post date: [September 27, 2025, 3:25pm UTC](https://discourse.paraview.org/t/vector-operations-in-python-calculator/17217/1 "2025-09-27T15:25:29Z")
Dear support,
I am struggling to perform some basic operations to get the moments around an axis. My objective is to find the normal force around an axis following this sketch:
Where AB is the axis that I’ve defined using a line filter and P is the point where a vector force is stored in my dataset.
The first step is to get the AP vector which works fine using this python calculator:
```auto
# Get reference to the inputs
surf = inputs[0]
axis = inputs[1]
# Get axis vector
A = axis.Points[0,:]
B = axis.Points[-1,:]
AB = B-A # VTKArray - Shape(3,)
AB = AB.reshape((3, 1))
# AP vector
AP = surf.Points-A # VTKCompositeDataArray - Shape(35248, 3)
return AP
```
And there you have the magnitude of the AP vector which increases as you get away from A
But then I need to perform dot and cross operations between the AB and AP vectors I the following code crashes:
```auto
# Get reference to the inputs
surf = inputs[0]
axis = inputs[1]
# Get axis vector
A = axis.Points[0,:]
B = axis.Points[-1,:]
AB = B-A # VTKArray - Shape(3,)
AB = AB.reshape((3, 1))
# AP vector
AP = surf.Points-A # VTKCompositeDataArray - Shape(35248, 3)
return cross(AB,AP)
```
Is it possible to get the cross and dot product of 2 vectors which belong to different filters in a simple way? I know how to do this using the regular calculators but I am trying to do this in a python calculator to simplify a bit my pipeline 😉
Thank you in advance for your time!
---
### Author:  [@Captain\_Convergence](https://discourse.paraview.org/u/Captain_Convergence)
#### Post date: [September 28, 2025, 4:41pm UTC](https://discourse.paraview.org/t/vector-operations-in-python-calculator/17217/2 "2025-09-28T16:41:14Z")
I’ve found a way to bypass this issue (after MANY tries) but I am a bit clueless of why this is the only solution that I could find so far:
```auto
import numpy as np
# Get reference to the inputs
surf = inputs[0]
axis = inputs[1]
# Get axis vector
A = axis.Points[0,:]
B = axis.Points[-1,:]
AB = B-A # VTKArray - Shape(3,)
# AP vector
AP = surf.Points-A # VTKCompositeDataArray - Shape(N Pts, 3)
# Bypass: Using an existing VTKCompositeDataArray,
# set it to 0 and sum your desired vector
AB_arr = AP * 0 + [AB[0], AB[1], AB[2]]
return cross(AP,AB_arr)
```
Also I’ve found another issue when using the “norm“ command to normalize the array that I had to bypass in a similar way. Instead of doing this:
```auto
n = norm(cross(AB_arr,r))
```
I have to do this:
```auto
# Bypass: Using an existing VTKCompositeDataArray,
# set it to 0 and sum your desired vector
Ones4dot_arr = AP * 0 + [1, 1, 1]
# Moment vector direction (n).
n = cross(AB_arr,r) / dot(Ones4dot_arr,Ones4dot_arr)
n = norm(n)
```
Is there any better/elegant way to perform these operations?
---
### Author:  [@Captain\_Convergence](https://discourse.paraview.org/u/Captain_Convergence)
#### Post date: [September 30, 2025, 5:44pm UTC](https://discourse.paraview.org/t/vector-operations-in-python-calculator/17217/3 "2025-09-30T17:44:11Z")
It would be very convenient to know how to declare new VTKArrays or VTKCompositeDataArrays inside the python calculator in an efficient manner to understand the structure of the data but I couldn’t find answers online 😃
---
### Author:  [@Captain\_Convergence](https://discourse.paraview.org/u/Captain_Convergence)
#### Post date: [November 5, 2025, 4:22pm UTC](https://discourse.paraview.org/t/vector-operations-in-python-calculator/17217/4 "2025-11-05T16:22:01Z")
No thoughts on any of this? 🙁