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. > >
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