MetPA: How to calculate Importance for pathway Impact

[PiRoMa]

Hi there,
can someone explain how exactly the Impact of a pathway is calculated in the tool metabolic pathway analysis (MetPA).

I know the following:
“MetPA uses relative betweenness centrality and out degree centrality measures to calculate compound importance. The pathway impact is calculated as the sum of the importance measures of the matched metabolites normalized by the sum of the importance measures of all metabolites in each pathway.” (doi: 10.1093/bioinformatics/btq418).

What I don’t know:
How are the ‘relative betweenness centrality’ and ‘out degree centrality’ combined to calculate the ‘Importance’.
Is it by addition or multiplication or division or …?

I thank you very much for the help.

[jeff.xia]

I don’t think the paper mentioned that the two measures are “combined”. They are separate measures. See below on the web interface for those options.

You can also examine the MetaboAnalystR code for exact details.

[PiRoMa]

Thank you very much, that helped me a lot.