[R] Prorating scale items

[Bob Green]

Hello,

I am hoping for some advice as to how I can prorate a number of scale
items that comprise a score. At least 69 of 159 cases have at least 1
value missing (65 cases have H7 missing). The maximum number of missing is
5.

I want to compute a total score, a score for the H items, the R items and
C items.

H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, C1, C2, C3, C4, C5, R1, R2, R3,
R4, R5

I am uncertain as to whether a series of IF statements are required or
some other strategy. Prorating is the method a researcher using this scale
has recommended.

Any advice is appreciated,

Bob Green