# PharmPK Discussion - Weighting factors with Excel

PharmPK Discussion List Archive Index page
• On 31 Aug 2006 at 16:53:02, Xiaodong Shen (shenxiaodong11.-a-.yahoo.com) sent the message
`The following message was posted to: PharmPKDoes anybody know how to using excel to do linearcalibration with a weighing factor 1/x or 1/x^2?ThanksXiaodong`
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• On 1 Sep 2006 at 08:55:00, "Elassaiss - Schaap, J. (Jeroen)" (jeroen.elassaiss.-at-.organon.com) sent the message
`The following message was posted to: PharmPKDear Xiadoing,In excel you just can calculate the sum of squares yourself and use thesolver for optimization. Then it is just a matter of dividing theresiduals by x^2 before squaring. (Prof. Derendorf showed me this trickto get PK fits in excel) But be aware that Excel's solver is not optimalfor PK(-PD) problems.Best regards,JeroenJ. Elassaiss-SchaapScientist PK/PDOrganon NVPO Box 20, 5340 BH Oss, NetherlandsPhone: + 31 412 66 9320Fax:   + 31 412 66 2506e-mail: jeroen.elassaiss.at.organon.com[At one point Solver was an optionally installed 'add-in' so you mayneed to revisit your installation disks to set it up. I found it inthe Tools menu of the Mac version - db]`
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• On 1 Sep 2006 at 10:19:14, "Kris Baert" (kris.baert.aaa.ugent.be) sent the message
`The following message was posted to: PharmPKHello Xiaodong,The most elegant way is by using the matrix calculation functions inexcel.The X matrix has two columns with 1 in the first column and the xvalues inthe second. The Y matrix has one column with the y values. The weightmatrixis a diagonal matrix with the 1/x or 1/x2 values. Then use thisformula tocalculate b and a (final matrix is one column, two rows). Don'tforget touse array formula's.=MMULT((MINVERSE(MMULT(TRANSPOSE(X);MMULT(W;X))));MMULT(TRANSPOSE(X);MMULT(W;Y)))Best regards,Kris--Kris Baert, DVM, PhDPharmacology, Toxicology, Biochemistry and Organ PhysiologyVeterinary Medicine - Ghent University`
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• On 1 Sep 2006 at 13:08:15, "Porzio, Stefano" (Stefano.Porzio.aaa.ZambonGroup.com) sent the message
`The following message was posted to: PharmPKDear Xiaodong,you can use, with prudence, the Excel "SOLVER" tool.An example of spreadsheets setup and calculations for nonlinearregression (obviously applicable to linear regression problems too)has been described in TiPS more than 10 years ago by Bowen and Jerman:Bowen WP, Jerman JC. Nonlinear regression using spreadsheets. TrendsPharmacol Sci. 1995 Dec;16(12):413-7.Best regardsStefanoDr. Stefano PorzioInpharzam Ricerche S.A. ZambonGroupTaverneSwitzerland`
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• On 1 Sep 2006 at 08:46:32, Mondelo Nelida (nmondelo.aaa.gador.com.ar) sent the message
`The following message was posted to: PharmPKYou could design your own spreadsheets employing Excel, taking intoaccountthe following references:Statistics for analytical chemistry, J.C Millar and Jn Millar  orSelecting the best curve fit, LC.GC Europe, 17 (3), 138-143,2004 Linearregression for calibration lines revisited: weighing schemes forbioanalytical methods, J. Chromatography B 774, 215-222,2002.Hoping to be of helpValeria Pongelli`
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• On 1 Sep 2006 at 11:48:17, "David S. Farrrier" (DFarrier.at.SummitPK.com) sent the message
`Xiaodong,PK Solutions is an Excel-based pharmacokinetics data analysis programthat makes PK analysis easy.The demo copy of PK Solutions illustrates the setup of a nonlinearregression analysis using the Solver add-in. To see this, downloadthe demo from www.SummitPK.com/pksolutions/pksolutions.htm (pre andpost Excel XP versions are available). Open the workbook to the"Curve Fit" spreadsheet tab. Click the "Curve Fitting Procedure"button for an explanation of how this works. Note that the demoillustrates the software in detail, but is disabled from performingpersonal data sets.Regards,David                                /\         /\        SummitPK.com      /\  /    \ /\  /   \                         /   /     /   /\   /  \=================================================David S. Farrier, Ph.D.          Phone:   970-249-1389Summit Research Services         Fax:    970-249-136068911 Open Field Dr.             Email:   DFarrier.-a-.SummitPK.comMontrose, CO 81401               Web:      http://www.SummitPK.com`
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