2017-05-23 02:13:31 -0500 received badge ● Scholar (source) 2016-06-17 11:08:00 -0500 received badge ● Necromancer (source) 2016-06-17 11:08:00 -0500 received badge ● Self-Learner (source) 2016-05-23 00:40:43 -0500 answered a question Expectation Maximization: logarithm likelihood > 0 I have asked this question on stack overflow and has been answered : http://stackoverflow.com/questions/14... Here is the copy of the answer given in stackoverflow: As I understand you have two separate GMMs for the foreground and background part of the image.The total probability of a sample pixel 'x' in the test image when evaluated in the foreground GMM is P_fg(x) = sum_over_j_1_to_k ( Wj_fg * Pj_fg( x )) where k = number of clusters in foreground GMM x = test sample Pj_fg(x) = probability that sample x is in j-th cluster according to the foreground GMM Wj_fg = weight of the j-th cluster in foreground GMM also, sum of all weights should be 1 for each GMM.  We can do a similar calculation for the background GMM. From looking at the EM code in opencv, it looks like the first part of the 2 values that EM returns is the log likelihood. For the foreground GMM this is  log(P_fg(x_i)) I implemented your algorithm and for each pixel in the test image, I compared the log-likelihoods returned for each of the two GMM-s and classified the pixel with the GMM with higher value. I got decent results. In that respect, yes this value is an indication of the pixel to be belonging to the entire GMM. 2) In my implementation of your problem, I always got the log likelihoods of all GMMS of all test-sample pixels under 0. 2016-01-25 01:06:15 -0500 received badge ● Enthusiast 2014-09-22 02:38:12 -0500 commented question Expectation Maximization: logarithm likelihood > 0 @CalumMurray I haven't discover any solution about that. I also post the question in stackoverflow http://stackoverflow.com/questions/14230377/opencv-output-of-the-predict-function-of-expectation-maximization But didn't get any success... If you find the solution, please post it, thank's. 2014-05-05 10:02:39 -0500 received badge ● Nice Question (source) 2013-02-20 20:43:16 -0500 received badge ● Supporter (source) 2013-02-20 19:45:55 -0500 received badge ● Critic (source) 2013-02-18 10:27:29 -0500 received badge ● Student (source) 2013-02-18 03:06:28 -0500 commented answer dot product Mat matrices Yes, you're right. Just I was confused that a dot product of matrices is a matrix multiplication which gives a matrix as output. And the dot product from openCV gives a scalar (as it treats matrices as vectors). But as OP is asking for cvDotProduct, there is no ambiguity. 2013-02-15 02:29:04 -0500 commented answer dot product Mat matrices For me, dot for matrices is matrix multiplication (I may wrong). Mat::dot is for vector in a Mat. Is the OP asking for a matrix multiplication or a dot between 2 vectors ? 2013-02-14 18:45:32 -0500 received badge ● Editor (source) 2013-02-14 18:41:07 -0500 asked a question Expectation Maximization: logarithm likelihood > 0 I try to find the propability of a pixel from one image (ImageCurrent.tif, see at the end) to belongs of the foreground and background of another image (ImageFormer.tif). Therefore, I create 2 GMMs (Gaussian Mixture Model) from one image with seperate foreground and background (using a mask). Then I used the predict function of the Expectation Maximization from OpenCV. When I get back the logarithm likelihood of the predict function, I have sometimes values >0 which is for me strange as the probability should be between 0 and 1 (so the log likelihood should be <=0). Is someone have experiment this kind of problem ? And how can I resolve it ? Here is a test program showing the problem: Mat mask = imread("mask.tiff", 0); Mat formerImage = imread("ImageFormer.tiff"); Mat currentImage = imread("ImageCurrent.tiff"); // number of cluster in the GMM int nClusters = 5; int countB=0, countF=0; Vec3b color; Vec2d probFg, probBg; // probabilities to belong to the foreground or background from GMMs //count the number of pixels for each training data for(int c=0; c<=40;c++) { for(int l=0; l<=40;l++) { if(mask.at(l, c)==255) { countF++; } else if(mask.at(l, c)==0) { countB++; } } } printf("countB %d countF %d \n", countB, countF); Mat samplesForeground = Mat(countF,3, CV_64F); Mat samplesBackground = Mat(countB,3, CV_64F); // Expectation-Maximization able to resolve the GMM and to predict the probability for a pixel to belong to the GMM. EM em_foreground= EM(nClusters); EM em_background= EM(nClusters); countB=0; countF=0; // fill the training data from the former image depending of the mask for(int c=0; c<=40;c++) { for(int l=0; l<=40;l++) { if(mask.at(l, c)==255) { color = formerImage.at(l, c); samplesForeground.at(countF,0)=color; samplesForeground.at(countF,1)=color; samplesForeground.at(countF,2)=color; countF++; } else if(mask.at(l, c)==0) { color = formerImage.at(l, c); samplesBackground.at(countB, 0)=color; samplesBackground.at(countB, 1)=color; samplesBackground.at(countB, 2)=color; countB++; } } } printf("countB %d countF %d \n", countB, countF); em_foreground.train(samplesForeground); em_background.train(samplesBackground); Mat sample(1, 3, CV_64F); // try every pixel of the current image and get the log likelihood for(int c=0; c<=40;c++) { for(int l=0; l<=40;l++) { color = currentImage.at(l,c); sample.at(0)=color; sample.at(1)=color; sample.at(2)=color; probFg=em_foreground.predict(sample); probBg=em_background.predict(sample); if(probFg>0 || probBg>0) printf("probFg %f probBg %f \n", probFg, probBg); } } ` I tried the program with the followings images: : http://postimage.org/image/eatsc71lj/ : http://postimage.org/image/sz4ona21j/ :http://postimage.org/image/xjquwak0v/ EDIT: Is this can be a bug from OpenCV ? As I'm not sure if it is normal or not, I don't know if I should open a ticket.