I want to compare GPML to GPflow, however GPflow uses the bernoulli distribution to perform classification. I was wondering if it's possible to do so in GPML. I cannot seem to find anything.
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I would train an alexnet DNN (given by MATLAB function alexnet) from scratch (i.e. without pretraining on ImageNet given by alexnet function). I could to manually set weights but I don't know the from what distribution I can sample my initial weights. Is there a built-in MATLAB option that make it for me?
For example, I've read that Python's library has the option pre-training=off but I don't find a similar option in MATLAB.
I am new to MATLAB and to LIBSVM. I got the fact that to use precomputed kernel, you must include sample serial number as the first column of the training and testing data. But importantly what I don't understand is: why would I use precomputed kernels? I am following the script described in LIBSVM and got results for linear and RBF but do not understand the need to use precomputed kernels.
Whether you need precomputed kernels depends on your metrics of input vectors. Sometimes you may need a different similarity function other than the norm-2 Euclidean distance or the radial basis function between a given feature to all the features from training set.
It is also possible that you need a multiplicative kernel (for example the product of two different kernel functions), which is not feasible by choosing one kernel type from Libsvm. Then writing a precomputed kernel is a good option.
Hi I'm trying to estimate the data distribution using Matlab.
For one dimensional data, I can definitely use ksdensity.
However my problems is that I need multi-dimensional joint distribution and conditional distribution.
I've tried kde tools from UCI. It is not functioning in my case and I cannot figure out why. So I'm asking for another tool I can possibly use..
Edit
The toolbox is not working and giving extreme results. I used 1e5 points and it might because the points are too dense.
KDE toolbox result
ksdensity result
Im a final year student working on my major project. My project is basically to extract text from a natural scene, and recognize it and then display them in a notepad etc..
I have already extracted the text form the images and have also obtained 85 features for each character which is extracted.
How ever, for the recognition part, I have no clue as of how to train or use SVM(support vector machines) in matlab so I can get a match.
Please help me out as this is turning out to be painstakingly difficult
If you're happy with using an existing SVM implementation, then you should either use the bioinformatics toolbox svmtrain, or download the Matlab version of libsvm. If you want to implement an SVM yourself then you should understand SVM theory and you can use quadprog to solve the appropriate optimisation problem.
With your data, you will need to have an N-by-85 feature matrix, where N is a number of characters, and an N-by-1 array of 'true labels' which you provide manually. Depending on which tool you use to train an SVM, the paramaters to svmtrain are slightly different - check the documentation.
If you want to evaluate your SVM to show that it works, you may need to organise your data such that you can estimate the generalization error of classifier - see cross-validation
I have a dataset for text classification ready to be used in MATLAB. Each document is a vector in this dataset and the dimensionality of this vector is extremely high. In these cases peopl usually do some feature selection on the vectors like the ones that you have actually find the WEKA toolkit. Is there anything like that in MATLAB? if not can u suggest and algorithm for me to do it...?
thanks
MATLAB (and its toolboxes) include a number of functions that deal with feature selection:
RANDFEATURES (Bioinformatics Toolbox): Generate randomized subset of features directed by a classifier
RANKFEATURES (Bioinformatics Toolbox): Rank features by class separability criteria
SEQUENTIALFS (Statistics Toolbox): Sequential feature selection
RELIEFF (Statistics Toolbox): Relief-F algorithm
TREEBAGGER.OOBPermutedVarDeltaError, predictorImportance (Statistics Toolbox): Using ensemble methods (bagged decision trees)
You can also find examples that demonstrates usage on real datasets:
Identifying Significant Features and Classifying Protein Profiles
Genetic Algorithm Search for Features in Mass Spectrometry Data
In addition, there exist third-party toolboxes:
Matlab Toolbox for Dimensionality Reduction
LIBGS: A MATLAB Package for Gene Selection
Otherwise you can always call your favorite functions from WEKA directly from MATLAB since it include a JVM...
Feature selection depends on the specific task you want to do on the text data.
One of the simplest and crudest method is to use Principal component analysis (PCA) to reduce the dimensions of the data. This reduced dimensional data can be used directly as features for classification.
See the tutorial on using PCA here:
http://matlabdatamining.blogspot.com/2010/02/principal-components-analysis.html
Here is the link to Matlab PCA command help:
http://www.mathworks.com/help/toolbox/stats/princomp.html
Using the obtained features, the well known Support Vector Machines (SVM) can be used for classification.
http://www.mathworks.com/help/toolbox/bioinfo/ref/svmclassify.html
http://www.autonlab.org/tutorials/svm.html
You might consider using the independent features technique of Weiss and Kulikowski to quickly eliminate variables which are obviously unimformative:
http://matlabdatamining.blogspot.com/2006/12/feature-selection-phase-1-eliminate.html