How to calculate Precision and Recall using confusion matrix in Matlab?

Question

I am working on 3 class problem.How to calculate precision,recall ,f-score,MCC of each class while using MATLAB. Here is my confusion matrix:

2775  0    0
1    591   0
4     0   845

I am calculating Accuracy from Confusion matrix in this way:

Accuracyy = 100*sum(diag(confusionMat))./sum(confusionMat(:));  

I want to measure below performance measures for each class.I know the formulas but how to execute this in MATLAB. Please help!!! I would really appreciate! Thank you!

1. Precision=TP / (TP + FP)

2. Recall= TP / (TP + FN)

3. F-score = 2*TP /(2*TP+ FP + FN)

4. Matthews Correlation Coefficient (MCC)

Answer 1

if yHat are your predictions and yval are your y true then

tp = sum((yHaT == 1) & (yval == 1));
fp = sum((yHaT == 1) & (yval == 0));
fn = sum((yHaT == 0) & (yval == 1));

precision = tp / (tp + fp);
recall = tp / (tp + fn);
F1 = (2 * precision * recall) / (precision + recall);

Answer 2

Here first find the all true positive value using diag function

tp_m = diag(cm_test);

and then for each class find the TP, TN, FP, FN using the following code

 for i = 1:num_labels
    TP = tp_m(i);
    FP = sum(cm_test(:, i), 1) - TP;
    FN = sum(cm_test(i, :), 2) - TP;
    TN = sum(cm_test(:)) - TP - FP - FN;

    Accuracy = (TP+TN)./(TP+FP+TN+FN);

    TPR = TP./(TP + FN);%tp/actual positive  RECALL SENSITIVITY
    if isnan(TPR)
        TPR = 0;
    end
    PPV = TP./ (TP + FP); % tp / predicted positive PRECISION
    if isnan(PPV)
        PPV = 0;
    end
    TNR = TN./ (TN+FP); %tn/ actual negative  SPECIFICITY
    if isnan(TNR)
        TNR = 0;
    end
    FPR = FP./ (TN+FP);
    if isnan(FPR)
        FPR = 0;
    end
    FScore = (2*(PPV * TPR)) / (PPV+TPR);

    if isnan(FScore)
        FScore = 0;
    end
end

Let me know if you need any assistance.