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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Analyzing/Modeling DynamoDB Usage

I'm seeking the correct mathematical tools to analyze/model a real world process for the purpose of optimizing resource allocation. I want to analyze consumed throughput of a AWS DynamoDB table and ...
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60 views

Mean value of discrete periodic signals

It is clear that a continuous periodic signal always takes at some point $x_m$ the absolute mean value. Then we could define the absolute mean value of the signal as the value that it takes at $x_m$. ...
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2answers
41 views

Finding simplest function to distinguish 2 sets

I wish to find a function that distinguishes $2$ sets. I have m data values in form of n-tuples out of which k are supposed to be mapped to a value less than $0$ and other m-k are supposed to be ...
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18 views

Enlarge a 2d plot of f(x,y) while keeping the moiré patterns at the same size

I have some function $z=f(x,y)$ with $x,y,z$ real numbers. I wrote a script that generates a $600\times 600$ pixels plot of this function for, say, $0 < x < 1$ and $0 < y<1$, by mapping z ...
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48 views

How can I minimize the error from fitting two functions to different parts of data?

I have some data, and I expect that part of the data will fit to a power law, and part of the data to a line. Here's a made up example of some similar data: Where I've made the red part a quadratic ...
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1answer
27 views

confusion in percentiles

in definition of percentile, it is said that, some value is in 30th percentile means, 30 percent of the data values are lower than the given value. But my confusion is, what if I have 1000 data ...
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17 views

different data fitting methods

I have a list of 2-dimensional points and I want to know different techniques of arriving at an approximate analytic relation between y and x. Also important would be to understand how one technique ...
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0answers
63 views

Predicting profit with price variation

I am currently working on a high school project that aims to predict profit from X amount of items to Y amount of profit based off a deviated sale price. For instance: I sale 10 cookies for 10 ...
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1answer
127 views

How to interpolate between sets of data

I'm probably using the wrong terminology, making it difficult to find a starting point. I have a set of motor data that looks like this: I can easily create a trend line for a given flow rate ...
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47 views

Minimum number of periods to determine periodicity

Is there a minimum window window length to determine true periodicity with a given estimated period. For example, if the same event is tested for every second and is observed twice at times 1 minute ...
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1answer
94 views

Interpreting 3 Circled Venn Diagrams

The Venn diagram above represents the 20 students who took one or more of the 3 available art classes or took no art classes at all. two students took no classes at all. 1.How many people take only ...
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1answer
88 views

Calculate 90th percentile of F distribution using “rchisq” function in R programming language

I am working on a problem for my Data Analysis class and I have to figure out a way to calculate the 90th percentile of the $F(3,5)$ distribution using the "rchisq" function in R(programming ...
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1answer
73 views

fastest and most efficent way to count all combinations in many sets and sum them together

I am a Java programmer who has reached the limits of brute computer power. My relational database (and non relational databases) is not producing results quick enough and I have hit a bottleneck in ...
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0answers
18 views

Find two clusters in an ordinated array

As the titles goes, I have an array of sorted real positive numbers, and some information on the structure of the data. I know that there are two constants $a>>b>0$ and two other numbers ...
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1answer
32 views

Chart Question and Percentages

The Venn Diagram above represents the 20 students who took one or more of the 3 available art class or took no art class at all. What percent of the students took only 1 art class? A. 10% B. 20% C. ...
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2answers
63 views

How to interpret the result of correlation between two discrete signals

Before starting, let me say I'm not a mathematician, I'm just a curious engineer, with a master's degree in engineering and computer science. I have been using this book The Scientist and Engineer's ...
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15 views

Does logged data have to be transformed back to its original form before testing the accuracy?

I have run my data through a model in r, i ran ARIMA to forecast. The model forces a log transformation to be applied to the data. To test the accuracy of the fitted model formed by ARIMA would i need ...
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34 views

Generalised chi square PDF: 2 normal DOF with different widths

I'm trying to derive the PDF $f_Z(x)$ for the random variable $Z = X^2 + Y^2$ where $X \sim N(0, \sigma_1)$ and $Y \sim N(0, \sigma_2)$. Searching here I've found this solution, which is only valid if ...
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1answer
90 views

Least squares fitting using cosine function?

Hello I am trying to fit a harmonic of the form $$y = b + c\cos(x)$$ to four data points (0,6.1) (.5,5.4) (1,3.9) (1.5,1.6) using least squares for homework. I know that the error $= Y_i - f(x_i)$ but ...
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1answer
22 views

What statistical analysis to use on a list of dates?

I suffer from migraines and for many years I've kept a log of each attack. I now want to do some analysis on the dates of each attack to see if there are any patterns. I intend to check the ...
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1answer
71 views

Queue and Stack in Computer Science and relation to MATH

For Creating a Queue Q we use two Stack S1,S2. for insert x in the end of Q we do Push(S1,x). for deleting element from front of Q, (if Q is not empty) we do Pop(S2). if on Q that at first is empty, ...
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69 views

Using significant figures, what would the answer be?

I've been learning about significant figures and I have a few questions. When you multiply/divide, the number of significant figures in the answer should be the same as the term with the least number ...
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1answer
53 views

How to find a graph's equation from its points

I have a set of data that constitutes the graph on the picture. What I want to know is how would I find the equation equivalent to that kind of graph? The X are on the interval $[1,10]$.
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1answer
59 views

Similarity measurement for strings of letters

Let's say, I have 10 different groups, and each group has its own string sequence. So, it should be like : G1 -> CHFAIEBD G2 -> HCFJIGBD G3 -> HCFAIJBD G4 -> HFCIJEBD G5 -> ..... G6 -> .... The ...
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1answer
32 views

Feature selection of Gabor filter

I am working with Gabor filter with level set method here. As you known, gabor filter gave many filter output. Some of them is not necessary. Could you suggest to me some method that can choose best ...
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3answers
51 views

fit sine wave to data

I have some astronomical data that I want to fit a sine wave to. I want to fit something of the form y = Asin(Ωt+Φ). I know the period of the sinusoid is equal to ...
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3answers
464 views

fit sine wave to data

I have some astronomical data which I know has a sinusoidal component to it of the form y = Asin(Ωt+Φ). The period of the sinusoid is equal to a sidereal day. So ...
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1answer
31 views

Find median given large amount of data

Listing all the possibilities would take time. Would there be a faster and more efficent way to find the median?
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1answer
50 views

How do you call it when you remove the top n% and the bottom n% of a dataset?

I am currently writing about a dataset of collected handwritings. I want to show some characteristics of the dataset. For example I think it is interesting to show how long it took users to create the ...
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2answers
51 views

Creating a polynomial function with no x-intercept

I have an understanding of polynomials and how to create a function based on the leading coefficient, degrees, x-intercepts, etc. My question is how do i go about creating a polynomial function that ...
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0answers
48 views

$y=\sqrt x \rightarrow \ln y = \ln x$ problem

So I had some raw data, and it looked like there was a square root relation. I plotted graphs of $y=\sqrt{x}$ They look kind of straight. So doing the algebra and taking the ln of both sides, we ...
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2answers
72 views

Finding similarity between elements using statistics

I have a dataset of DJs in which I'm trying to find DJs similar to a specific DJ. Each DJ has a set of a genres with a certain percentage. How can I find the similarity between 2 DJs? The following is ...
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1answer
279 views

Median value resulting in negative number

I know the that the formula for finding the median of grouped data that is: $$\mathrm{Median} = L_m + \left [ \frac { \frac{n}{2} - F_{m-1} }{f_m} \right ] \times c$$ And I also know what the ...
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1answer
46 views

Data interpretation problem

Approximately what is the minimum amount of caffeine, in milligrams, consumed per day by a person who daily drinks two 10-ounce mugs of percolated coffee and one 12-ounce cup of a caffeinated ...
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1answer
35 views

Multidimensional fitting of two data sets

My problem is the following: A laser gives out a bunch of data points which are reflected off a metal surface and recorded by a camera attached to the side of the laser. The image the camera receives ...
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1answer
52 views

Finding a population Function

I have been given the population of the USA from 1790 - 1980 (increasing in intervals of $10$) and I am asked to solve this differential equation. Using $t$ as time in years, and $P$ as size of ...
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1answer
49 views

Formula to link two exponential values together - doesn't quite work

Basically, I've done a script, and I'm stuck on a formula for it. After I run the code on a cube, based on two different inputs (detail level and vertex average iterations), the resulting size will be ...
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1answer
29 views

Work out if the relationship between 2 datasets is constant

I have 2 one-dimensional datasets, let's call them a and b. I want to know the correlation between ...
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0answers
167 views

How do you use R to find the box counting dimension of a two dimensional set of data, or scatter plot?

I'm using the software R to do some analysis on some data sets for a graduate project. R has a package called "fractaldim", in this package is a function for finding the box counting dimension. The ...
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1answer
40 views

Is there a way to use the Generalized Mean to find the “best” possible mean to use for a specific data set?

I've recently learned about the Generalized Mean as an abstraction of the many different means, includeing the Geometric, Arithmetic, and Harmonic means, as well as others. It is my understanding ...
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1answer
32 views

Survival analysis in survey dropouts?

I am working with a survey data set and am curious about who abandoned it before finishing all the questions. I have information on how many questions each respondent answered (no skipping allowed) ...
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0answers
45 views

Form of a function I can fit like a polynomial that has an asymptote on x-axis and is always positive

So I have a small list of pairs of the form $(\mathbb{R}, \mathbb{R}_{\geq 0})$ and I want to fit a function to this data. Additionally I know that as $x$ grows large in either direction $y$ tends to ...
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1answer
102 views

What is purpose of correlation kernel? IIs it high pass filter or low pass filter?

I am research about correlation kernel and I have some questions that need your help. Let see the pp. 3302-3303 in the http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6517250&tag=1 The special ...
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39 views

Linear model for data that follow gaussian distribution

I have a question about linear regression. We have the linear regression of input data $(X,Y)=((x_1,y_1),(x_2,y_2)...(x_n,y_n))$ is $$F=aX+b$$ a,b are factors of the linear line, $y_i$ is {-1,1}. ...
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1answer
2k views

Finding the range from standard deviation and Gaussian Curve

The figure above shows a normal distribution with mean m and standard deviation d, including approximate percents of the distribution corresponding to the six regions shown. Suppose the heights of a ...
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1answer
27 views

How to determine who improved the most considering diminishing returns

My friends and I are competing in a fitness challenge against each other. We will determine the winner based on who has the greatest percentage improvement after three months. Here is the problem: if ...
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1answer
34 views

Method for detecting anomalies in timeseries?

I am exploring creating alerts for anomalies in a timeseries. Say that I have a graph like this: There are two anomalies here that I would wanted to be alerted on: First, on April 7th with there ...
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0answers
54 views

How to interpret the indicator function?

I am reviewing a paper titled " Bayesian Sampling Approach to Decision Fusion" by Biao Chen and Pramod K Varshney. This paper uses an indicator function that I am not being able understand. The ...
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141 views

Betfair Odds Percentage Movements & Hedging

I want to determine if the odds on Betfair have decreased by a certain percentage and then calculate the hedged profit when hedging on that percentage, but it's made tricky by the fact that decimal ...
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2answers
193 views

How to find a line that minimizes the average squared perpendicular distance from the given points to the line?

I have set of points scattered around the origin. How to find a vector, such that the average squared distance (perpendicular distance) from points to the vector is minimised? Added For example, ...