# How to calculate Finite Strain Tensor using Python Calculator?

Hi,

I’d like to calculate the large deformation strain tensor in a 3D deforming model. The formula is as follows:

where x’ is the reference/initial coordinate, and the deformed coordinate x = x’ + u. I tried with Compute Derivates and Gradients filter, however, I think these 2 filters can only take derivates of the deformed coordinates x. Is there a way to take derivates of x’?
I used the Calculator filter to compute x’ = x - u, but I cannot find a function in both Calculator and Python Calculator with can let me compute du/dx’. Anyone has any ideas?