Confusion Matrix for ECOC model classification Example

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AbioEngineer 2019-8-21

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https://ww2.mathworks.cn/matlabcentral/answers/477082-confusion-matrix-for-ecoc-model-classification-example

评论： AbioEngineer 2019-8-31

采纳的回答： Gaurav Garg

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Running this example in the Command Window:

openExample('textanalytics/CreateSimpleTextModelForClassificationExample')

Is there any way of creating a Confusion Matrix for a cross validated version of the above ECOC model? Similar to this example:

openExample('stats/TrainECOCClassifiersUsingEnsemblesAndParallelComputingExample') 

Is the problem with the type of Learner during the fitECOC step? or is it because the class labels are contained in a cell array of strings, and are non-numeric like in the second example?

the error I get when using crossval is that the first input argument must be 'mse', 'mcr', or a function handle. I am trying to do a simple classification of only 2 classes, so I'd expect a 2x2 confusion matrix. I don't think I need start a parallel pool or use a very complicated learner for my NLP text classification.

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Answer 1

Gaurav Garg 2019-8-29

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https://ww2.mathworks.cn/matlabcentral/answers/477082-confusion-matrix-for-ecoc-model-classification-example#answer_389569

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Hi,

In my understanding, you wish to know a way to create a confusion matrix for the example textanalytics/CreateSimpleTextModelForClassificationExample.

You can use confusionmat function which compute confusion matrix for classification problems. For the above example, the following code shall give you the confusion matrix -

[cm,grp]=confusionmat(YTest,YPred)

And as far as 2x2 confusion matrix is concerned, since you have multiple classes, you are expected to receive a matrix of dimensions nxn where n is the number of classes. In the output matrix, cell (i,j) denotes the class i which has been labelled as class j.