# Questions tagged [data-mining]

This tag is for questions about data mining, which is an interdisciplinary subfield of computer science. It is the computational process of discovering patterns in large data sets.

104 questions
2answers
101 views

### How do I find the formula (or rules) that created a list of numbers with seemingly no pattern?

Newbie here, and I apologize if this is the wrong forum for this type of question... I have a group of 200 or so alphanumeric codes from an unknown source. Here's an example piece of the data set: <...
1answer
5k views

### Normalization of data in decision tree

After reading through a few references, I have come to know that for machine learning in general, it is necessary to normalize features so that no features are arbitrarily large ($centering$) and all ...
1answer
5k views

### Mutual Information for clustering

I'm working on a document clustering application and decided to use Normalized Mutual Information as one of the measures of effectivenes. But I don't really understand how to implement this in that ...
1answer
65 views

### How to find almost periodic lattices in a set of high-dimensional points?

sorry for lame question, but I just have no maturity in this direction. Let's say I have very large set ( millions ) of high-dimensional vectors ( typical dimensionality is 64). These vectors ...
1answer
458 views

### What is KL-Divergence? Why Do I need it? How do I use it?

I am currently studying KL Divergence. But It seems very confusing that I don't maybe understand why do I ever need it and what is that for? As I have been reading stuff about Mutual Information, it ...
2answers
1k views

### Distance between unequal-dimension vectors (and data)?

It is easy to find simple distance measures for equal-dimension vectors, such as Euclidean Distance or Correlation. What about unequal-dimension vectors, such as, for instance, $(a,b,c)$ and $(d,e)$? ...
1answer
2k views

### How can one prove that mahalanobis distance is a metric?

How can one prove that mahalanobis distance is a metric? How can one show that these four properties of a metric are valid for mahalanobis distance? 1) d(x, y) ≥ 0 (non-negativity, or separation ...
0answers
45 views

### Number of rules (Data Mining)

This is a paraphrasing of a statement from Data Mining by Witten et al., 4th edition, on section 1.6. Consider the set $S = \{1, \dots, 288\}$. A rule is defined as a one-element singleton set ...
0answers
212 views

### Does there exist closed-form solutions for calculations in the EM-algorithm for Gaussian Mixtures?

Our data can be represented as $X_{n\times d}$ matrix, where we have $n$ data points lying in $\mathbb{R}^d$. We assume that there are $k$ underlying Gaussian models, $\mathcal{N}_d(\mu_j, \Sigma_j)$, ...
1answer
35 views

### Clustering elements according to covariance matrix

I'm doing a little bit of topic modelling (which is not really my area) with twitter tweets. The situation is the following: I have a (sort of) covariance matrix where the entrie $C_{ij}$ corresponds ...
0answers
355 views

### Gini coefficient vs Gini impurity - decision trees

The problem refers to decision trees building. According to Wikipedia 'Gini coefficient' should not be confused with 'Gini impurity'. However both measures can be used when building a decision tree - ...
2answers
173 views

0answers
19 views

### Matching Metric - How to Normalize for different Amounts in Equation

I'm a non-mathematician. I'm trying to find if tweets are on topic with news articles algorithmically. Part of this involves taking each word from every tweet and seeing if it's in the news articles ...