How to compute accuracy for cluster evaluation in Weka

Question

How do we compute accuracy for clusters using Weka?

I can use this formula:

Accuracy (A) = (tp+tn)/Total # samples

but how can I know what is the true positive, false positive, true negative and false negative in the output of experiment in the Weka tool?

Accuracy is not a common evaluation measure for clustering. What is "true positive", what is "true negative"? — Has QUIT--Anony-Mousse, Mar 18 '15 at 04:18

score 1 · Answer 1 · answered Mar 17 '15 at 16:48

There are a few different clustering modes in Weka:

Use training set (default): After clustering, Weka classifies the training instances into clusters it developed and computes the percentage of instances falling in each cluster. For example, X% in cluster 0 and Y% in cluster 1, etc.

Supplied test set: It is possible with Weka to evaluate clusterings on separate test data if the cluster representation is probabilistic like EM algorithm.

Clustering evaluation using classes: In this mode Weka first ignores the class attribute and generates the clustering. During testing, it assigns class labels to the clusters on the basis of the majority value of the class attribute within each cluster. Finally, it computes the classification error and also shows the corresponding confusion matrix.

To do that you need to know the actual clusters assigned to each data point. In that case you can ude the third method which is very similar to classification. — Rushdi Shams, Mar 17 '15 at 22:02

score 0 · Answer 2 · answered Oct 13 '15 at 14:30

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Take a look on cross-validation principles. Use ClusterEvaluation 's methods crossValidateModel and evaluateClusterer in your java code. Or you can also experiment that with the weka GUI directly.

answered Oct 13 '15 at 14:30

marilena.oita

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score 0 · Answer 3 · answered Mar 26 '20 at 10:50

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Based on this answer to a similar question the classificationViaClusteringmeta classifier which can be downloaded through the package manager will do what you want.

answered Mar 26 '20 at 10:50

MikeF

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How to compute accuracy for cluster evaluation in Weka

3 Answers3

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