Please note that the result is not interpolated into uniform mesh by the product.
you can use "find". For example, you want to find a slice z=z0, you can use
Ex0=Ex(:,:,find(z,z0),1)
where Ex is a 4D matrix in xyz and f. Some of them are singleton. the above method uses the single frequency result.
you can also specify a small length, eg
Ex0=Ex(:,:,find(z,z0):find(z,z0+1e-6),1)
It would be much simpler to specify the region in the GUI using script as you did.
You are navigating away from the AIS Discovery experience