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*To*:*Multiple recipients of list <coredmg@iucr.org>***Subject**:**Expressions for R factors****From**:**Brian McMahon <bm@iucr.org>***Date*:*Fri, 4 Sep 1998 11:44:39 +0100 (BST)**Reply-To*:*coredmg@iucr.org*

John Bollinger at Indiana writes: > With regard to _refine_ls_wR_factor_*: it seems unusual to me that the > sum in the denominator is over Y(calc) instead of over Y(obs). Is this > intentional, and if so, can you refer me to any literature about why this > particular usage is to be preferred? I have never run into it before, and I > shall have to make special provisions to get my software to calculate it. I > see that this formula appears in the version 2.0.1 dictionary as well, but > that does not invalidate the question. For example, the definition of _refine_ls_wR_factor_all is ( sum | w | Y(obs) - Y(calc) |^2^ | )^1/2^ wR = ( --------------------------------- ) ( sum | w Y(calc)^2^ | ) as against the definition for _refine_ls_R_factor_gt, which is sum | F(obs) - F(calc) | R = ------------------------ sum | F(obs) | I note that the original definition for _refine_ls_wR_factor_ in version 1.0 of the Core read wR = [sum(w|Ym-Yc|^2^) / sum(wYm^2^)]^1/2^ Have we simply introduced a typo into later versions? Brian

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