Dear all,
How to obtain correlation matrix (using GSAS)? Is there any option with
EXPGUI?
regards,
Santosh Babu
On Tue, Apr 8, 2008 at 8:33 PM, Brian H. Toby <[EMAIL PROTECTED]> wrote:
> The sign of the numbers indicates correlation vs. anticorrelation. For
> example, Uiso's correlate between atom 1 and 2 in phase "1 1 1UISO" &
> "1 2UISO" so that Uiso increasing on one atom has a similar impact as an
> increase on the other. In the case of the reciprocal cell tensor (related to
> cell parameters) an increase on one of the diagonal terms has a similar
> effect as a decrease on the zero correction ("1 RM11" & "ZERO 1").
>
> Brian
>
>
> On Apr 8, 2008, at 8:55 AM, Leopoldo Suescun wrote:
>
> Dear Gerard,
> Here is how to read it:
>
> The correlation matrix terms greater than 0.50 are
> 1 1UISO-1 2UISO 5011 3UISO 687 1HSCL 801
> 1 2UISO- 1HSCL 650
> 1 3UISO- 1HSCL 852
> 1 RM11-ZERO 1 -642
> 1 RM22-ZERO 1 -640
> 1 RM33-ZERO 1 -692
> 1ABS1- 1ABS2 1000
> 1 1PF 2-1 1PF 3 -727
> v-cov distribution 0...1 by 0.05
> 430 125 77 34 7 10 7 2 0 1 1 0 2
> 3 1 0 1 1 0 1
>
>
> 1st column (8 characters wide): Variable 1, 2nd column: (also 8
> characters wide) Variable 2, with "-" separating both columns, 3rd
> column (6 characters wide) the correlation value multiplied by 1000.
> Following collumns are show if more paramters have correlations greater
> than 0.5 with the parameters in the first collumn. So in this case, 4th
> collumn (8 characters wide with no separation from 3rd): Variable 2',
> 5th collumn (6 char wide): correlation between Var1 and Var2', etc for
> var 2''...
>
> So you can read the first column this way:
> 1 1UISO (Iso thermal param. for atom 1 in phase 1) shows a correlation
> of 0.501 with 1 2UISO (iso param for atom 2 in phase 1) so thermal
> parameters for atoms 1 and 2 inphase one have 50% correlation.
> 1 1UISO shows .687 corelation with 1 3UISO, or atom's 1 and 3 Uisos
> are correlated 68.7%
> 1 1UISO is correlated with histogram scale factor by 80.1 %
>
> ABS = absorption correction if my memory is good but you can check in
> the GSAS manual that accompanies GSAS distribution. You have a problem
> with the setup of the refinement because you have 2 absorption
> corrections and both parameters are correlated by 100% so they are not
> refining independently. I don't remember what the numbers before and
> after ABS mean (histogram, phase, model applied) but check in the manual
> and you'll find it.
>
> The last line, v-cov distribution 0...1 by 0.05 shows the values in a
> histogram with range of covariances from 0 to 1 divided in classes 0.05
> wide. First value means that 430 pairs of parameters show absolute value
> of correlation between 0.0 and 0.025, 2nd value means 127 parameters
> show absolute value of correlation between 0.025 and 0.075 and so forth.
>
> The top list only gives those higher than 0.5 in absolute value so you
> expect 10 counting the last 10 entries in the bottom line, as shown.
>
> Hope this helps.
> Leo
>
> Dr. Leopoldo Suescun
> Argonne National Laboratory
> Materials Science Division Bldg 223
> 9700 S. Cass Ave. Argonne IL 60439
> Phone: 1 (630) 252-9760
> Fax: 1 (630) 252-7777
>
> ----- Original Message -----
> From: "Gerard, Garcia S" <[EMAIL PROTECTED]>
> Date: Tuesday, April 8, 2008 7:37 am
> Subject: correlation matrix interpretation
>
> Dear all,
>
> Could you please help me to translate this chunk of the correlation
> matrix?HSCL is the histogram scale factor
> PF profile coefficients
> RMii lattice parameters
> ABS?
> UISo thermal parameters
>
> how do i interpret the numbers? and the signs? how strongly
> correlated these variables are?
>
> regards
>
>
>
>
> --
> Heriot-Watt University is a Scottish charity
> registered under charity number SC000278.
>
>
> <leopoldo.vcf>
>
>
> ******************************************************************** Brian
> H. Toby, Ph.D. office: 630-252-5488
> Materials Characterization Group Leader, Advanced Photon Source
> 9700 S. Cass Ave, Bldg. 433/D003 work cell: 630-327-8426
> Argonne National Laboratory secretary (Marija): 630-252-5453
> Argonne, IL 60439-4856 e-mail: brian dot toby at anl dot gov
> ********************************************************************
>
>
>
