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R for Classification Jennifer Broughton Shimadzu Research Laboratory Manchester, UK jennifer.broughton@srlab.co.uk 2 nd May 2013

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Classification? Automatic Identification of Type (Class) of Object from Measured Variables (Features) Object TypeFeature1Feature2Feature3…….Feature n Label 1val[1,1]val[1,2]val[1,3]……. val[1,n] Label 2val[2,1]val[2,2]val[2,3]…….val[2,n] ………….…….…….…….……… Label mval[m,1]val[m.2]val[m,3]…….val[m,n] 2 of 17

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Example Data 3 of 17

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Data Preparation & Investigation EDA Technique Box Plots PCA Decision Trees Clustering Training Set Best features to distinguish between classes Relationships between features Feature reduction 4 of 17

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Box Plots PCA & Multivariate Analysis: ade4 FactoMineR 5 of 17

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Example Classifier 6 of 17

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Classification Algorithms in R Rattle: R Analytical Tool to Learn Easily ( Rattle: A Data Mining GUI for R, Graham J Williams, The R Journal, 1(2):45-55 ) 7 of 17

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SVM 8 of 17

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Ensemble Algorithm 9 of 17

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Training and Testing Classification Algorithm: Neural Network Support Vector Machine Random Forest Training Set (labelled) Test Set (unlabelled) Trained Classifier Classification Results Prediction Results + Labels Assess Predictions: Confusion Matrix ROC Curve (2 categories) …. 10 of 17

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Using Classifiers in R Select Training Data Build Classifier Run Classifier classifier algorithm(formula, data, options) (boosting and nnet) classifier.pred predict(classifier, newdata, options) 11 of 17

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SVM & Neural Net Tuning 12 of 17

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Classifier Feedback print(classifier) plot(classifier) high Gini Coefficient = high dispersion 13 of 17

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Classifier Prediction Results predict(type = “class”) predict(type = “prob”) confusion matrix 14 of 17

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False Negative False Negative True Positive True Positive True Negative True Negative False Positive False Positive Binary Classification Results Y N Class Present? Class Detected? Y N 15 of 17

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ROC Curves in R ROCR package 16 of 17

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Example Results 17 of 17

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