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Chemometric functions in Excel
Oxana Rodionova & Alexey Pomerantsev Semenov Institute of Chemical Physics
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Distance Learning Course in Chemometrics for Technological and Natural-Science Mastership Education
Unfulfilled need in chemometric education in Russia Low number of qualified specialists in chemometrics Large distances, e.g. Moscow – Barnaul is about 3000 km No modern chemometrics books in Russian No available chemometric software No support from officials: government, Academy, etc 3000 km Easy available everywhere => INTERNET Interactive layout: all calculations should be clear and repeatable Web friendly environment for the calculations => EXCEL Necessity to make and use our own (free) software => EXCEL Add-In 4000 km Barnaul
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Chemometric calculations in Excel
Provides user with all possibilities of Excel interface, worksheet calculations, worksheet functions, charts, etc. VBA helps to simplify routine work All calculations are made "on the fly“ and very fast
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Installation http://rcs.chph.ras.ru/down/sacs.zip
Chemometrics.dll put in your Windows folder (C:\WINDOWS\) Chemometrics. xla put in the AddInn folder (C:\Documents and Settings\ <User>\Application Data\ Microsoft\AddIns\) Load Chemometrics.xla by < Excel Options> <Add-Ins> in the open Workbook
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Matrix calculations in Excel
={TRANSPOSE(B6:F10)} Ctrl-Shift-Enter B6:F10 Barr ={MMULT(B6:F10,TRANSPOSE(Barr))}
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Principal Component Analysis (PCA)
Initial data = + × Error matrix E I J A Score matrix T I Loading matrix X P J A PT J A I J X=TPT+E
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Chemometrics XLA. PCA Scores
Xcal Xtst Centering AND/OR weighting ={ScoresPCA(Xcal,5,1,Xtst)} nPC
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Chemometrics XLA. PCA Loadings
Xcal Excel worksheet function =TRANSPOSE(LoadingsPCA(Xcal,5,1))} nPC Centering AND/OR weighting
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List of chemometric functions
PCA ScoresPCA <for calibration or test samples> LoadingsPCA PLS ScoresPLS <X-scores for calibration or test samples> UScoresPLS <Y-scores for calibration or test samples> LoadingsPLS <P-loadings> WLoadingsPLS QLoadingsPLS PLS2 ScoresPLS2 <X-scores for calibration or test samples> UScoresPLS2 <Y-scores for calibration or test samples> LoadingsPLS2 <P-loadings> WLoadingsPLS2 QLoadingsPLS2 Options: Centering AND/OR scaling Number of PCs
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X data (calibration set)
ScoresPCA X data (calibration set) ScoresPCA (rMatrix [, nPCs] [,nCentWeightX] [, rMatrixNew] ) Number of PC (A) Test set centering and/or scaling 1 centering 2 scaling 3 both X[IJ] T[I A]
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10% -out cross-validation
Validation Rules If rMatrixNew is omitted then only calibration scores are calculated If rMatrixNew is specified then only test scores are calculated If rMatrixNew coincides with rMatrix then cross-validation is calculated 10% -out cross-validation
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X data (calibration set)
LoadingsPCA X data (calibration set) LoadingsPCA (rMatrix [, nPCs] [,nCentWeightX]) Number of PC (A) centering and/or scaling 1 centering 2 scaling 3 both X[IJ] P[J A]
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Explorative Data Analysis
Case study 1: People
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People
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Dataset in Excel Workbook (People.xls)
Number of objects (n) = 32 Number of variables (m) = 12
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Data Preprocessing Aim: to transform the data into the most suitable form for data analysis
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Autoscaling mean centering scaling autoscaling + =
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People: Scores & Loadings (PC1 vs. PC2)
“Map of Samples” “Map of Variables”
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People: Scores & Loadings (PC1 vs. PC3)
Loading plot Score plot
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Case study 2: HPLC-DAD
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Measurements
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Dataset in Excel Workbook
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If we observe X can we predict C and S ?
Pure compounds A and B If we observe X can we predict C and S ? X=CST+E
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Score plot A B
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Conclusions from the Score Plot
1. Linear regions = Pure compounds 2. Curved line= Co-elution 3. Closer to the origin = Lower intensity 4. Number of bends = Number of different compounds
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Factor analysis vs. PCA analysis
X E1 + = C ST × 2 J I X E2 + = T PT × A J I
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Scores and Loadings
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Procrustes transformation
X ≈ CST X ≈ TPT I = RRT = Identity matrix X ≈ T(RRT)PT = (TR)(PR)T C ≈ TR S ≈ PR R = Rstretch ×Rrotation ^ ^
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Scores Transformation
Stretching Rotation
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Procrustes analysis results
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Conclusions Scaling and centering is problem dependent
In this example number of PCs = Number of different compounds
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Regression
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Principal Component Regression (PCR)
1 t A ... P T X 1) PCA y T a = + e 2) MLR
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Projection on Latent Structures (PLS)
Q U P T W p 1 t A ... X u 1 A ... q t Y w 1 t A ...
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Projection on Latent Structures (PLS)
B = + e Y
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PLS and PLS2 b = + e y T 1 PLS B = + E Y T M PLS2
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ScoresPLS X[IJ], Y[I1] T[IA]
X data (calibration set) Y data (calibration set) ScoresPLS (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY] [, rMatrixXNew]) Number of PC (A) X Test set centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ], Y[I1] T[IA]
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UScoresPLS X[IJ] , Y[I1] U[I A]
X data (calibration set) Y data (calibration set) UScoresPLS (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY] [, rMatrixXNew] [, rMatrixYNew]) Number of PC (A) X Test set Y Test set centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ] , Y[I1] U[I A]
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WLoadingsPLS X[IJ] , Y[I1] W[J A]
X data (calibration set) Y data (calibration set) WLoadingsPLS (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY]) Number of PC (A) centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ] , Y[I1] W[J A]
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LoadingsPLS X[IJ] , Y[I1] P[JA]
X data (calibration set) Y data (calibration set) LoadingsPLS (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY]) Number of PC (A) centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ] , Y[I1] P[JA]
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QLoadingsPLS X[IJ], Y[I1] Q[1 A]
X data (calibration set) Y data (calibration set) QLoadingsPLS (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY]) Number of PC (A) centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ], Y[I1] Q[1 A]
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ScoresPLS2 X[IJ], Y[IK] T[I A]
X data (calibration set) Y data (calibration set) ScoresPLS2 (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY] [, rMatrixXNew]) Number of PC (A) X Test set centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ], Y[IK] T[I A]
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UScoresPLS2 X[IJ], Y[IK] U[I A]
X data (calibration set) Y data (calibration set) UScoresPLS2 (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY] [, rMatrixXNew] [, rMatrixYNew]) Number of PC (A) X Test set Y Test set centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ], Y[IK] U[I A]
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LoadingsPLS2 WLoadingsPLS2 QLoadingsPLS2
X data (calibration set) Y data (calibration set) LoadingsPLS2 (rMatrixX, rMatrixY [, nPCs] [, nCentWeightX] [, nCentWeightY]) Number of PC (A) centering and/or scaling of X 1 centering 2 scaling 3 both centering and/or scaling of Y 1 centering 2 scaling 3 both X[IJ], Y[IK] P[J A] or W[J A] or Q[K A]
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Seventh Winter Symposium on Chemometrics
near Tula city, February 2010 100 km
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