how to plot a graph

Question

nkumar 2014-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/162792-how-to-plot-a-graph

评论： Star Strider 2014-11-15

I want to plot ROC sensitivity vs specitivity,I have calcuated all these parameters for 3 class problem,now kindly tell how to plot roc crve

results are

 Actual Classes
-------------1--------2--------3-----
    TP |   38.00 |   50.00 |   50.00
    FP |   12.00 |   0.00 |   0.00
    FN |   0.00 |   12.00 |   0.00
    TN |   100.00 |   88.00 |   100.00
Preci. |   0.76 |   1.00 |   1.00
Sensi. |   1.00 |   0.81 |   1.00
Speci. |   0.89 |   1.00 |   1.00
------------------------------------------
Model Accuracy is 0.92

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Answer 1

Star Strider 2014-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/162792-how-to-plot-a-graph#answer_159035

Use the perfcurve function.

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nkumar 2014-11-15

在 MATLAB Online 中打开

 i tried this but could not plot it ,[x,y]=perfcurve();here i get x,y as only four values,where mu input to this function is 44 values

Star Strider 2014-11-15

You have to give it the raw results of your classification, not the confusion matrix summary results you posted. I assume you have the classification results it requires. See the documentation on Performance Curves for a detailed discussion.

From that documentation:

perfcurve is intended for use with classifiers that return scores, not those that return only predicted classes. As a counter-example, consider a decision tree that returns only hard classification labels, 0 or 1, for data with two classes. In this case, the performance curve reduces to a single point because classified instances can be split into positive and negative categories in one way only.

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