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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79 views

On the truncation of spherical harmonics

Suppose there is a function $f(\theta,\phi)$ defined on the surface of a sphere, and $\theta$ and $\phi$ are the polar and azimuthal angles respectively. Similar with the fact that a function defined ...
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1answer
67 views

Is topological data analysis useful for low dimensional data?

I often read how Topological Data Analysis (TDA) is useful especially for highly dimensional data. But, what about (apparently) low dimensional ones? Example: consider measuring the resistance of a ...
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1answer
46 views

Calculating Inflection Point in Real World Data

I can think of a few ways to get a good grasp of this problem from an experimental perspective, but I'm looking for a more general explanation that can be applied to different situations. If this ...
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1answer
36 views

Data Analysis and Probability

Two dice with a difference ... They appear identical, but one die is fair and the other is loaded so that the probability of throwing a 6 is 0.25. Bev picks a die at random and throws it, and it shows ...
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1answer
35 views

How to work out the formula that connects several numbers

I have an interesting problem. Say I have lots of datasets like this: a = 21 b = 23 c = 58 d = 498 etc (lots of other values) X = 85 I need to find the formula ...
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2answers
744 views

Where to start learning about topological data analysis

I was wondering if anyone could help me out with finding a nice introductory introductory text for topological data analysis (I'm speaking as somebody who has two semesters of experience with ...
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1answer
183 views

Extremely poor polyfit, what am I doing wrong?

I have a dataset with me: http://pastebin.com/YZArky1j, which I am trying to polyfit. This is what I used to perform the polyfit: ...
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1answer
66 views

Smoothing Spline Example

I am learning the smoothing spline method. I saw that smoothing spline is a penalty term to reduce overfitting in linear regression. Given dataset {$(x_1,y_1),(x_2,y_2)..(x_n,y_n)$}So the formular ...
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2answers
391 views

Probability of name collision

Question on statistics & probability: I am trying to find the best way to build a unique key. Data i have: 1) first name 2) last name 3) DOB 4) gender So, assuming those are correct fields (not ...
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0answers
29 views

Effect of Event on Another

I am having difficulty wrapping my mind around conceptualizing the impact of one event on another. For the scope of this question, let's define the following: Event A: An assault occurs; Event B: A ...
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0answers
36 views

Bivariate Correlation Unique solution

I have a set of data, let's say "score vs loss ratio", the score is an arbitrary number I gave to a team by looking at their past history. I want to prove my hypothesis which is higher the score, high ...
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1answer
47 views

Variance of Estimated Coefficients in Logistic Regression

I have a logistic regression model with a binary variable as the response and a categorical variable with 3 categories as a predictor. The fitted model is: logit(P(Y=1)) = intercept -0.19*C2 + ...
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1answer
48 views

Empirical Copula

I am trying to find the empirical copula linking two random variables $X$ and $Y$. I have some data available but it's limited with respect to the variable $Y$ and I am not convinced it's enough data ...
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1answer
48 views

Data compression from lack of patterns

From my understanding, lossless data compression takes advantages of statistical patterns. I want to know if it is possible to compress data based on the lack of patterns, such as a random string of ...
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1answer
31 views

How do I creat a box and whisker plot?

I know you have to create a box around the median of a data set of numbers, but I do not know where the end of the box would be placed. Please help!
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1answer
27 views

Addition of two box plots

I have two box plots that I'd like to add together to form one box plot representing both plots in one. Here's an example of two box plots: At a school 200 boys and 200 girls participated in a test. ...
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0answers
18 views

Best multivariate approximation scheme for scattered data approximation

what is the best multivariate approximation scheme for scattered data approximation on a set E of points in $R^d$?
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0answers
44 views

Find spikes in data

I have some datasets and I need to find spikes in them. Imagine the data looks like trading data. If the spike is big enough, I need to log it, otherwise, proceed in the analysis. I tried with a ...
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1answer
18 views

Is Expectation Propagation (EP) affected by the prior?

I understand EP by reading Minka's thesis: http://research.microsoft.com/en-us/um/people/minka/papers/ep/minka-ep-uai.pdf I'm trying to apply it to solve a Bayesian inference problem. However, I'm ...
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1answer
271 views

slope of curve represented by discrete points

I have data which are visualized in this chart: I need to compute slope of increasing / decreasing parts of the curve. I can't use any 2 points because of noise in data. Maybe numerical derivative ...
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1answer
33 views

Problem with significant figures

I know that if I am multiplying/dividing my answer is the least number of significant figure in the data and if I am adding/subtracting my answer is the least number of decimal places i the data but ...
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1answer
154 views

Maths concept for salient point in graph data

I have collected data concerning the total post counts of users in an online forum (see graphic). What I am hoping to do is compare the language of 'first posts' with the language of 'later posts'. ...
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0answers
39 views

Simple maths for an algorithm to searching a table to find out if one type of entry has a causal effect upon another type?

I asked this over on StackExchange and was sent over here... I have a database table which is recording two different types of events which seem to be related to one another. It records the date and ...
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1answer
138 views

Given a set of data points, how to use gradient descent to find the minimum in the function that passes from those data points?

I have a function with n parameters. I don't know the formula of the function but I can generate as many data points as I want using the function that I have. My question is, how can I find the set of ...
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1answer
28 views

Correct equation

What is the correct equation which describes the following dates: 270, 180, 135, 112.25, 101.25. I've obtained data whit the equations: 180 + 90 = 270 135 + 45 = 180 112.5 + 22.5 = ...
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0answers
27 views

How to compute a “weather” score for repeated trials over time, with a bias for recency

I'm doing some analysis on repeated software tests that can either pass or fail. For each test, I've collected a set of historical (pass/fail, timestamp) records, and I'd like to compute a score to ...
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1answer
43 views

Distance measures for binary data

I was wondering what are some good distance measures for binary data that have the following properties. I know that there are measures like the Jaccard index and the Dice Index, but they don't ...
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1answer
176 views

Sigmoid function with separate control of derivative at 0 and sharpness of bend.

For a physical relationship, $f(x)$, I'm trying to model, i have a fairly good determination of some of the boundaries, such that $ f(0) = 0$ $f'(0) = B$ $ \lim_{x\to\infty} f = A $ So far, what I ...
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1answer
104 views

How to appropriately normalize financial data?

I am evaluating a normalization of financial data. Two colleagues feel certain of a certain approach, and I am befuddled. The approach shapes the results how they want (i.e., brings possibly extreme ...
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1answer
275 views

Analyzing data to determine seasonal indices?

The quarterly sales levels for the past four years of a leading tyre manufacturer are displayed on the table table How to analyze the data to determine the specific seasonal indices,and what ...
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0answers
258 views

Kalman filter with sensors having different sampling rate

I would like to implement Kalman filter scheme with two different kind of sensors - say 9DOF IMU (gyro/accelerometer/magnetometer) and GPS sensor (position/velocity/altitude). Problem is, as i ...
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1answer
119 views

Looking for data science-oriented “Applied Maths for dummies” summer school

I'm a PhD candidate who critically lake of maths skills for his data science projects. I'm looking for a summer school that would enable me to take off in this aspects. This could be ...
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2answers
155 views

2D data fitting

I have some numbers as a function of 2 variables: $(x, y) \mapsto z$. I would like to know which function $z=z(x,y)$ best fits my data. Unfortunately, I don't have any hint, I mean, there's no ...
2
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1answer
620 views

Is there a scientific way to assign weights to historical data?

This is a common question I usually face while processing historical data. I have year on year data of an event for the past N years.I would like to assign weights to the data of these N years so that ...
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0answers
58 views

Is it possible to get function from bunch of points?

I have some points which I know the position in 3D. and that points made in sequence. for example, . (x1,y1,z1) ...
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1answer
63 views

matching two curves

I have two curves extracted from some data and I'm trying to detect when there is a difference. Each of these 3 plots represents a different data set. From these example curves below, I'm looking for ...
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1answer
42 views

How to convert one number range to another? (Prioritizing a list of skills based on current familiarity and usefulness)

I'm trying to come up with a formula to prioritize a list of skills that a learner should tackle based on: current familiarity with the skill, and the usefulness of the skill. Familiarity is a $1$ ...
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0answers
108 views

Two Part Question Regarding Function Analysis and Encryption

I've been to my professors office hours, and my teaching assistants are not making this clear for me. Encryption is such a great field of study and I really would like to get off on the right foot. ...
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3answers
95 views

$4\log_2(n)=n$ How to Solve for $n$?

As the title suggests, my log skills are pretty lacking. Need to learn how to get from $4\log_2(n)=n$ to $n=16$ ($\log$ base $2$). I've searched Google and it seems I am missing some core concept ...
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1answer
42 views

Decision to market one or the other game, based on the expected demand

For example, there is a new video game to market, lets call it Game 1, and there is a 0.60 probability that its competitor will produce a new game similar to it. (This 0.60 may not need to be known ...
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0answers
47 views

Approximating a probability distribution given multiple datasets

I am beginner in mathematics/statistics and apologise in advance for my faulty use of language. I am working on a problem in statistical genetics. Given a dataset, $D$, I obtained probabilities for ...
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0answers
19 views

Correct sampling methods for this data set / requirements

I am just looking for a push in the right direction as to what kind of sampling methods I can use to fulfill this set of sampling criteria. I had thought stratified sampling, but I'm not sure if ...
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4answers
63 views

Finding function for data

I'm in need of a function for this data which occurs in an application I am making. I've been staring at it for hours and I can't figure it out, hope someone here can help me. Here's the data: f(x) = ...
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1answer
73 views
2
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1answer
29 views

Aproximate data with this equation (or linearize the equation)

I have found an equation that describes the behaviour of a phisical system: $$ y=a_1e^{-a_2x} + a_3 + a_4x + a_5e^{{-a_6} / {(1-x)}}$$ Now I have data of that physical system and I want to ...
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4answers
143 views

Predicting the movement of people on a grid.

Let there be a $30$ by $30$ grid that is there are $900$ tiles.The rows are numbered from 1-30 while the columns are numbered from (i) to (xxx). There are total of $100$ people and each of them is ...
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3answers
58 views

Separating populations and estimating line-fit parameters

Given a dataset containing two populations, each of which can be described by a linear relationship between two variables in each sample with high R$^2$, how does one separate the two populations (and ...
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2answers
73 views

Can we express “exactly X” with set theory?

I have a question that I think that is a better fit here than a programming SE as SQL is founded on set theory and my question is more about set theory than about a programming question. Assuming I ...
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2answers
47 views

Scaling data into $[-1,1]$

I have a data in the matrix for: \begin{bmatrix} 1 & 2 & 3 & 9 & 6\\ 8 & 2 & 7 & 4 & 6 \\ 1 & 2 & 8 & 7 & 4 \end{bmatrix} Each row corresponds ...
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2answers
56 views

Best way to generalize a distribution of data into smaller subsets?

Suppose I had a data set as follows: 168.95, 176.83, 178.13, 179.61, 179.44, 172.83, 173.37, 174.06, 174.94, 175.43, 175.73, 175.5, 173.78, 174.06, 172.71, 174.3, 178.38, 178.43, 177.18, 175.34, ...