Bayes Error Rate Matlab
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Naive Bayes Matlab
(view profile) 8 questions 0 answers 0 accepted answers Reputation: 0 on 25 Sep 2016 at 22:25 Latest activity Edited by Massimo Zanetti Massimo Zanetti (view profile) 0 questions 63 answers 34 accepted answers Reputation: 174 on 26 Sep 2016 at 7:17 12 views (last 30 days) 12 views (last 30 days) I am new to machine learning and i have derived general expressions for naive bayes matlab code bayes decision boundary and trying to plot the graph for mu=1 and sigma^2=2; Trying to plot a figure which contains both class conditional pdfs p(x|ωi) and posterior probabilities p(ωi|x) with the location of the optimal decision region. I should also obtain the bayes error rate for it. Can someone please help me? This is what i have tried so far:%Plott Class-Conditional fplot( @(x) ( (1/sqrt(2*pi)) * exp(- (x.^2)/2) ) ,'Linewidth',2); hold on; fplot( @(x) ( (1/(2* sqrt(pi))) * exp( - (x.^2 - 2*x +1)/4) ) ,'Linewidth',2); hold off; legend({'P(x|w1)','P(x|w2)'}, 'FontSize',14) xlabel('x' ,'FontSize', 12) ylabel('p(x|wi)' , 'FontSize', 12) title('Graph of class conditional pdfs p(x|wi)', 'FontSize', 14) %Plott Posterior fplot(@(x) ( ((1/sqrt(2*pi)) * exp(- (x.^2)/2))/( ((1/sqrt(2*pi)) * exp(- (x.^2)/2)) + ((1/(2* sqrt(pi))) * exp( - (x.^2 - 2*x +1)/4)) ) ) ) hold on; fplot(@(x) ( ((1/(2* sqrt(pi))) * exp( - (x.^2 - 2*x +1)/4)) / ( ((1/(2* sqrt(pi))) * exp( - (x.^2 - 2*x +1)/4)) + (( (1/sqrt(2*pi)) * exp(- (x.^2)/2)) ) ))) hold off; 1 Comment Show all comments Massimo Zanetti Massimo Zanetti (view profile) 0 questions 63 answers 34 accepted answers Reputation: 174 on 26 Sep 2016 at 7:17 Direct li
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Optimal Bayes Error Rate
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Description Construction Methods Properties Copy Semantics Examples References How To This is machine translation Translated by Mouse over text to see original. Click the button https://www.mathworks.com/matlabcentral/answers/304455-obtaining-bayesian-error-rate below to return to the English verison of the page. Back to English × Translate This Page Select Language Bulgarian Catalan Chinese Simplified Chinese Traditional Czech Danish Dutch English Estonian Finnish French German Greek Haitian Creole Hindi Hmong Daw Hungarian Indonesian Italian Japanese Korean Latvian Lithuanian Malay Maltese Norwegian Polish https://www.mathworks.com/help/stats/naivebayes-class.html Portuguese Romanian Russian Slovak Slovenian Spanish Swedish Thai Turkish Ukrainian Vietnamese Welsh MathWorks Machine Translation The automated translation of this page is provided by a general purpose third party translator tool. MathWorks does not warrant, and disclaims all liability for, the accuracy, suitability, or fitness for purpose of the translation. Translate NaiveBayes classNaive Bayes classifierexpand all in pageNaiveBayes will be removed in a future release. Use fitcnb to create a ClassificationNaiveBayes object instead.DescriptionA NaiveBayes object defines a Naive Bayes classifier. A Naive Bayes classifier assigns a new observation to the most probable class, assuming the features are conditionally independent given the class value.ConstructionNaiveBayesCreate NaiveBayes objectMethodsdispDisplay NaiveBayes classifier objectdisplayDisplay NaiveBayes classifier objectfitCreate Naive Bayes classifier object by fitting training dataposteriorCompute posterior probability of each class for test datapredictPredict class label for test datasubsasgnSubscripted reference for NaiveBayes objectsubsrefSubscripted reference for NaiveBayes objectPropertiesCIsNonEmptyFlag for non-empty classesClassLevelsClass levelsDistDistribution namesNClassesNumber of classesNDi
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site http://stackoverflow.com/questions/9967089/misclassification-error-rate-and-accuracy About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Misclassification error rate error rate and accuracy up vote 2 down vote favorite Below is a Matlab code for Bayes classifier which classifies arbitrary numbers into their classes. training = [3;5;17;19;24;27;31;38;45;48;52;56;66;69;73;78;84;88]; target_class = [0;0;10;10;20;20;30;30;40;40;50;50;60;60;70;70;80;80]; test = [1:2:90]'; class = classify(test,training, target_class, 'diaglinear'); % Naive Bayes classifier [test class] (a) If someone could provide code snippets for calculating the Bayes error for misclassification and accuracy. I went through matlab's documentation regarding bayes error rate [class,err]=classify(...). But, I am unable to follow it and work. (b) Also, how to plot a scatter plot and histogram indicating the number of data points belonging to different classes? I tried out with scatter(training(:),target_class(:)) but it gives something else! (c) How to work with crossvalidate()? An example would really help.Thank you. classification matlab pattern-recognition share|improve this question edited Apr 2 '12 at 1:11 asked Apr 1 '12 at 18:34 Chaitali 70110 add a comment| 1 Answer 1 active oldest votes up vote 2 down vote accepted (a) To calculate misclassification error you need to know test_class as well. Then you can compare the output class variable with test_class. misserr = sum(test_class~=class)./numel(test_class); If you don't have the test classes the 2nd output argument err will give you an estimate for misclassification error applying generated model on the training set. (b) If you have just 2 factors (columns) in the training data set you can just do scatter(training(:,1),training(:,2),[],target_class) Correspondingly, you can use SCATTER3 for 3 factors. For more factors you can perform Principal Component Analysis with PRINCOMP and plot 2 or 3 first components. UPDATE: I missed that you actually have only one factor.
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