[Bug]: Index error when finding the cell centered coordinates of a slice

[wk9874]

What happened?

When attempting to get the global values of a slice using to_global, I get the following error:

  File "test.py", line 5, in <module>
    sim.slices[1].to_global()
  File "lib/python3.10/site-packages/fdsreader/slcf/slice.py", line 537, in to_global
    base_coord = next(iter(self._subslices.values())).get_coordinates(ignore_cell_centered=False)[dimension][0]
  File "lib/python3.10/site-packages/fdsreader/slcf/slice.py", line 66, in get_coordinates
    co += abs(co[1] - co[0]) / 2
IndexError: index 1 is out of bounds for axis 0 with size 1

I think this is due to the mesh along one axis only having one coordinate in the FDS file:

&MULT ID='m1', DX=1.25,DZ=0.5 I_UPPER=7,K_UPPER=1/ 16 mesh
&MESH IJK=100,1,40, XB=0,1.25,-0.1,0.1,0,0.5, MULT_ID='m1'/

And the last coordinate being removed in get_coordinates before the shift is performed:

            if self.cell_centered and not ignore_cell_centered:
                co = co[:-1]
                co += abs(co[1] - co[0]) / 2

Steps to reproduce

1. Run the Pohlhausen validation case: https://github.com/firemodels/fds/blob/master/Validation/Convection/FDS_Input_Files/Pohlhausen_Pr_1.fds
2. Try to load the temperature slice from the results:

import fdsreader

sim = fdsreader.Simulation("pohl_results")

temp_slice = [slice for slice in sim.slices if slice.quantity.quantity == "TEMPERATURE"][0]

values = temp_slice.to_global()

FDS version used

6.9.1

fdsreader version used

1.11.7

[JanVogelsang]

I don't have an immediate solution right now, as implementing the to_global method correctly for all possible scenarios is quite difficult, as the data FDS outputs is not very consistent and has plenty of edge cases.

In the meantime until a solution is found, maybe you don't need to use to_global for your use case, but can instead just iterate over the subslices (there is one subslice per mesh) and analyze the slice per mesh instead. This is not only more robust and flexible, but also much faster (in some cases).