Relative Strength Formula

[1angel2]

Hi,

I know the standard RS is just price of stock divided by market average. But I've seen in Stan Weinstein's book where the RS line can have negative values as well with a zero line. Can the formula be something like:

(%change of stock) / (%change in market average) or

(%change of stock) - (%change in market average) ?

Or is the standard version clearer?

Thanks