Thank you all for the information and F estimator write-up.
With regards
Karthik
On 13-03-2017 03:56 AM, Phil Evans wrote:
Sorry Ian, I was attributing this to Kevin
apologies
Phil
On 12 Mar 2017, at 21:56, Ian Tickle wrote:
Eleanor,
Phil is right about the bias of the weighted mean,
Hi Eleanor
I reran my simulation including your method. Let's just look at the two
extreme cases in my original table: sd(F+) = 10, sd(F-) = 1 (5th row) and
sd(F+) = 1000, sd(F-) = 100 (last row: the case where my method performs
worst but still better than the others!). I used the same 'true' v
Eleanor
I notice that you are calculating a weighted mean using 1/sd(I) as the
weight whereas in least squares one would of course normally use
variance-weighting, i.e. 1/sd(I)^2. I assume this is intentional and is a
way to reduce the bias effect of weighting, so that the resulting bias of
the m
Sorry Ian, I was attributing this to Kevin
apologies
Phil
> On 12 Mar 2017, at 21:56, Ian Tickle wrote:
>
>
> Eleanor,
>
> Phil is right about the bias of the weighted mean, here's how I do it using a
> minimum mean-squared error estimator which seems to give more accurate
> results than e
Thanks Ian.
e
On 12 March 2017 at 21:56, Ian Tickle wrote:
>
> Eleanor,
>
> Phil is right about the bias of the weighted mean, here's how I do it
> using a minimum mean-squared error estimator which seems to give more
> accurate results than either the unweighted or the weighted mean:
>
> http:/
Eleanor,
Phil is right about the bias of the weighted mean, here's how I do it using
a minimum mean-squared error estimator which seems to give more accurate
results than either the unweighted or the weighted mean:
http://staraniso.globalphasing.org/Optimal-F-estimator.pdf
This is actually about
It should be the unweighted mean to avoid bias towards I+ or I-
(or Kevin Cowtan had a more complicated way)
Phil
> On 12 Mar 2017, at 17:58, Eleanor Dodson wrote:
>
> You read:
> h k l IPLUS SIGIPLUS INEG SIGINEG
> Then program calculates this:
>
>SIGIMEAN = SIGIPLUS*S
You read:
h k l IPLUS SIGIPLUS INEG SIGINEG
Then program calculates this:
SIGIMEAN = SIGIPLUS*SIGINEG/(SIGIPLUS+SIGINEG)
IMEAN = (IPLUS/SIGIPLUS + INEG/SIGINEG)*SIGIMEAN
ie: IMEAN = ( IPLUS*SIGINEG + INEG * SIGIPLUS ) / /(SIGIPLUS+SIGINEG)
Is that the right thing
Dear CCP4bb,
How IMEAN and SIGIMEAN is calculated in scalepack2mtz if the input is
with anomalous intensity (obtained from HKL2000). Any guide/reference is
highly appreciated.
Thanks in advance,
With regards
Karthikeyan S.
Principal Scientist
IMTECH, Chandigarh
