Change HDF5 file attribute from 'dx,dy,dz' to 'dx_dy_dz'

docs/source/output.rst

@@ -17,8 +17,8 @@ The output file has the following HDF5 attributes at the root (``/``):
 * ``gprMax`` is the version number of gprMax used to create the output
 * ``Title`` is the title of the model
 * ``Iterations`` is the number of iterations for the time window of the model
-* ``nx, ny, nz`` is a tuple containing the number of cells in each direction of the model
-* ``dx, dy, dz`` is a tuple containing the spatial discretisation, i.e. :math:`\Delta x`, :math:`\Delta y`, :math:`\Delta z`
+* ``nx_ny_nz`` is a tuple containing the number of cells in each direction of the model
+* ``dx_dy_dz`` is a tuple containing the spatial discretisation, i.e. :math:`\Delta x`, :math:`\Delta y`, :math:`\Delta z`
 * ``dt`` is the time step of the model, i.e. :math:`\Delta t`
 * ``srcsteps`` is the spatial increment used to move all sources between model runs.
 * ``rxsteps`` is the spatial increment used to move all receivers between model runs.
@@ -161,7 +161,3 @@ The ``#geometry_view:`` command produces either ImageData (.vti) for a per-cell
     * You can turn on and off the visibility of materials using the eye icon in the Pipeline Browser. You can select multiple materials using the Shift key, and by shift-clicking the eye icon, turn the visibility of multiple materials on and off.
 
     * You can set the Color and Opacity of materials from the Properties panel.
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