Features used by Percolator

Following is a list of the features used by the crux percolator command to represent each peptide-spectrum match (PSM).

Number	Name	Type	Description
1	lnrSp	Float	The natural logarithm of the rank of the match based on the Sp score
2	deltLCn	Float	The difference between this PSM's XCorr and the XCorr of the last-ranked PSM for this spectrum, divided by this PSM's XCorr or 1, whichever is larger.
3	deltCn	Float	The difference between this PSM's XCorr and the XCorr of the next-ranked PSM for this spectrum, divided by this PSM's XCorr or 1, whichever is larger. Note that this definition differs from that of the standard delta Cn reported by SEQUEST®.
4	Xcorr / XCorr Score	Float	The SEQUEST cross-correlation score
5	Sp / Sp score	Float	The preliminary SEQUEST score.
6	IonFrac	Float	The fraction of b and y ions theoretical ions matched to the spectrum
7	Mass	Float	The observed mass [M+H]+
8	PepLen	Integer	The length of the matched peptide, in residues
9-11	Charge[n]	Boolean	Is this a 1+/2+/3+ charged spectrum?
12	enzN	Boolean	Is the peptide preceded by an enzymatic (tryptic) site?
13	enzC	Boolean	Does the peptide have an enzymatic (tryptic) C-terminus?
14	enzInt	Integer	Number of missed internal enzymatic (tryptic) sites
15	lnNumSP	Float	The natural logarithm of the number of database peptides within the specified precursor range
16	dM	Float	The difference between the calculated and observed mass
17	absdM	Float	The absolute value of the difference between the calculated and observed mass