## Comet parameter: precursor_charge

- This parameter specifies the precursor charge range to search.
- This parameter expects to integer values as input.
- If the first input value is 0 then this parameter is ignored and all charge states are searched
- Only in the case where a spectrum does not have a precursor charge will all charges in the specified charge range be searched.
- If the first input value is not 0 then all charge states between (and inclusive of) the first and second input values are searched. Again, only for those spectra with no specified precursor charge state.
- If a precursor charge is present for a particular spectrum, this parameter will not override that charge state and that spectrum will always be searched.
- With the default "0 0" values and a spectrum with no precursor charge, Comet will either search the spectrum as a 1+ or a 2+/3+.
- The default value is "0 0" if this parameter is missing.

Example:
`precursor_charge = 0 0` search all charge ranges
`precursor_charge = 0 2` search all charge ranges (because first entry is 0)
`precursor_charge = 2 6` search 2+ to 6+ precursors
`precursor_charge = 3 3` search 3+ precursors