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comment Feature extraction based on correlations
How many voxel's are you looking at this could quickly get computationally intractable, quite quickly. Efficiency in this context is also a function of how much time are you willing to wait, and what computational resources you have access too. Intuitively I don't see what you are really trying to do with these correlations, what does the PCA of these things do for you?
May
17
answered How to reset options to default in SAS 9.3?
May
17
revised Calculate Significance between samples with skewed data
html broken
May
17
comment Calculate Significance between samples with skewed data
I'm just a bit confused about why you are trying to subsample, since you already have a larger sample. Are you trying to determine sample size for a future sample?
May
17
revised reasons for a non-invertible matrix
added an example
May
17
answered reasons for a non-invertible matrix
May
16
awarded  Tumbleweed
May
16
comment Rescaling Features for ML
The problem with k-means is that no matter how you scale the data, you will always have issues with outliers. Using a log transform should work, but this may change the relationships between your variables considerably. You may also want to take a look at k-medoids or other more robust classifiers.
May
14
comment How to make sure that a machine learning algorithm's implementation is correct?
That was sort of the point. If you have a black box with a few examples and no binary to deconstruct, you are frankly out-of-luck. If this is a 'novel' method and there is a paper you can reproduce the program to the best of your ability, and that's about it. If you have a binary, but can't reproduce the results because of some initial values, you should at least know what object the initial values are (vector, scalar), and check how sensitive the algorithm is to choice of initial values.
May
14
answered Calculate Significance between samples with skewed data
May
14
comment What are the real benefits of normalization (scaling values between 0 and 1) in statistics?
A lot of the answers are with respect to normalization (standardization), if this isn't what you are looking for could you please expand on how you are normalizing (scaling) your data. Are you just scaling the score range over the interval 0,1?
May
14
revised Sequential Probability Ratio Test (or other Sequential Sampling techniques) for testing difference
This is hypothesis testing not a proof.
May
13
suggested approved edit on Sequential Probability Ratio Test (or other Sequential Sampling techniques) for testing difference
May
13
comment Joint or marginal?
I think you should go over your terms a bit, $(\theta_1, \theta_2, \theta_3)$ is not a distribution, in this case it is a random variable, it has a distribution. When you say marginal, what does that mean, what are the other variables you are integrating out? (I'm pretty sure you are working with a Gibb's sampler and trying to interpret the output, but let's be clear about what's going on here). So let's define our terms and fill in some details then we can probably answer this.
May
13
awarded  Yearling
May
13
revised How to make sure that a machine learning algorithm's implementation is correct?
spelling and other things
May
13
answered How to make sure that a machine learning algorithm's implementation is correct?
May
13
comment How to make sure that a machine learning algorithm's implementation is correct?
This doesn't seem to be a model issue, but an implementation issue.
May
13
comment How to make sure that a machine learning algorithm's implementation is correct?
I think this is fairly good advice, if you want to work with a closed implementation of an existing algorithm you first need to check the sources which includes finding the paper used in the algorithm. If there aren't published peer review papers on the algorithm I would be suspicious about using it in the first place. The next issue I would look at is to find several simple examples, that you can work out easily then check the program against them. A final method is to email the author, there is a human that wrote this code and she should be able to help you out.
May
11
reviewed No Action Needed Error of the variance