def get_feature_names_chem(peplen):
    """
	feature names for the fixed peptide length feature vectors
	"""
    names = []
    names += ['pmz', 'peplen', 'ionnumber', 'ionnumber_rel', 'mean_mz']
    for c in ['mean_{}', 'max_{}', 'min_{}', 'max{}_b', 'min{}_b',
        'max{}_y', 'min{}_y']:
        for b in ['bas', 'heli', 'hydro', 'pI']:
            names.append(c.format(b))
    for c in ['mz', 'bas', 'heli', 'hydro', 'pI']:
        names.append('{}_ion'.format(c))
        names.append('{}_ion_other'.format(c))
        names.append('mean_{}_ion'.format(c))
        names.append('mean_{}_ion_other'.format(c))
    for c in ['plus_cleave{}', 'times_cleave{}', 'minus1_cleave{}',
        'minus2_cleave{}', 'bsum{}', 'ysum{}']:
        for b in ['bas', 'heli', 'hydro', 'pI']:
            names.append(c.format(b))
    for i in range(peplen):
        for c in ['mz', 'bas', 'heli', 'hydro', 'pI']:
            names.append('fix_' + c + '_' + str(i))
    names.append('charge')
    return names
