electron spectra (dQ/dE versus energy (MeV)

Hello,
I would like to make electron spectra dQ/dE versus energy (MeV) for any r position.

I saw many beautiful spectra from FBPIC in scientific journals.
I unsuccessfully found a script in openpmd_viewer but I looked for it online for weeks.

Could anyone help me please?
Fred
In addition, how can we retrieve the information about electron angular spread?