Which RDF curve represents NH–O(water) interaction in polymer–water system?

Dear All,

I calculated the RDF between the NH group in my polymer and the oxygen atom in water using MS. The RDF output shows three curves: Total NH, Total WO, and Total NH-WO (as in the screenshot). Which of these should I use to correctly represent the RDF between the polymer NH group and water oxygen atoms?

Thanks 

Hakkim