# Tagged Questions

Questions on the use of mathematical techniques to extract properties from given data. Consider if your question might be more suited for Cross Validated (stats.SE) instead.

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### Slightly convoluted problem I need help solving involving the percent change formula.

I was hoping someone knows the solution or has an alternative form of approach. tried this out over on /r/askmath with little response. Ok I will attempt to be as clear and as simple as possible. I ...
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### Probability of a Collision in Selection of Permutations

Suppose I have a set of characters, say $\{a-z,A-Z,0-9\}$ $(n=62)$. Then I select a random permutation each containing $10$, e.g. $k=10$, characters. What would be the probability of a collision &...
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### Deal with circular standard deviation

I have a sensor that gives me a direction of the target in degrees with a certain standard deviation and I use a circular probability density function (PDF) to represent probable locations for the ...
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### Inversion of the Burrows Wheelers Transform

The "Burrows-Wheeler Transform" in signal processing is a transformation which is used in for instance data compression and pattern recognition. It can be described in mathematical terms as: Start ...
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### 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 ...
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### Methods for Extrapolating Data Close To Observations

I am aware of many different ways to go about interpolating between the values of known data points. However, whenever I come upon (I work in Quantitative Finance) the need to extrapolate data I find ...
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### Random data generation from a bivariate distribution

Let $X$ and $Y$ be non negative random variables with joint distribution $$F(x,y)=1-e^{-x}-e^{-y}+e^{-x-y-\delta xy}; ~~~x\geq 0,~~y\geq 0.$$ How to generate a bivariate ...
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### Parameters estimation for gaussian function with offset

I've read the paper Least square fitting of a Gaussian function to a histogram by Leo Zhou on how to perform a Least Square Fitting of a gaussian function to a histogram. The Gaussian function used ...
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### Way to compare three numbers with an algorithm.

Say I have values 10, 3, 6 What would be a way of finding a subjective difference between them. Or in other words, how close they are to each-other. So if i had 3, 2.5, 2.8; they would be close ...
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### make the mean of 2 data sets the same

I am in the process of computing my student's final scores and for some reason I couldn't figure this step out: If I have 2 data sets of scores in the range [0,40] but one data set has a different ...
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### Representing a Concept

From Formal Concept Analysis: If I have a set of objects: G={Shark, Penguin, Bat} and a set of attributes: M={Breathe Underwater, Can Fly, has Vertebrae} and I make a chart to represent my ...
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### Using Excel to calculate relative difference between three numbers

Background I am trying to produce a table of values for the positioning of the hands of a clock at any time, limited by one second intervals, to demonstrate the feasibility of an ultra precise, ...
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### Function to convert all -ve numbers into their +ve counterparts without affecting present +ve values (-12 to 12)

I am essentially after a function that will convert negative values in my Excel spreadsheet into their positive equivalents without affecting the present positive values. A sample of my data would ...
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### Interpreting Entropy

All you data scientists will probably know the entropy equation: $$H(p)=-\sum_{i=1}^{n}{{p}_{i}}\cdot\log_{2}{{p}_{i}}$$ And, using this, I was messing around with some compression, and calculated ...
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### What measurement should be used to determine per unit capacity of a given volume ish question

I am reselling data packages and would like to add a sense of scale to the packages. Without disputing actual numbers, an email message is between (3-20)Kbytes, a photo 270kb, a web page (.25-1.5)...
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### How to verify how good my data is?

I'm in an undergrad physics lab right now and I have taken some data. The theoretical curve should be proportional to $\cos^2(\theta)$. How can I quantify how close my data values are to this ...
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### Are there any programs like family echo that I can use to map mathematics?

Family echo is an online program that allows one to make a family tree, if nothing is clicked it shows most of the family tree as it is, but if one clicks a name one can see clearly all the ancestors ...
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### There are 2 red, 3 pink, 4 orange, and 5 yellow jelly beans in the pocket. how many different ways can you choose at least one jelly bean?

Thanks a lot!There are 2 red, 3 pink, 4 orange, and 5 yellow jelly beans in the pocket. how many different ways can you choose at least one jelly bean?
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### What property of $n$ does this test?

I have the following sample data: 1 true 3 false 12 false 10 true 7 true 9 false 8 false My question is, what property of ...
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### Detecting periodic patterns in data - how often are the meetings held?

Suppose some people I know frequently have meetings, and suppose I want to find out whether there's a pattern to when these meetings take place, and if so how often they occur. I can take note of the ...
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### How can non-binary data be tested for distinguishability from random?

Given a large string of Base-N digits (in other words, not necessarily binary), is there software or an algorithm that can output whether the data is reasonably pseudorandom or reveals a pattern? In ...
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### comparing empirical data to a model prediction using exponents

I am not a mathematician, but I have a basic question about comparing numbers with exponents near $1$. I am evaluating how well a "model" works and I want to make a compelling case. For example, my ...
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### Predicting the increase/decrease of number

I have these entries in my database that looks like this: ...
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### How can I infer order from partially ordered discrete sequences?

A really interesting problem that I can't stop thinking about! Have run in to this a couple of times but yet to find a smart approach to either solve or frame this problem. This is my try at ...