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.

learn more… | top users | synonyms

0
votes
1answer
15 views

How do I calculate the function of an (expected) logarithmic distribution, if I know the area under the curve & one data point?

I'm trying to get the function that lets me determine the value of y, where x is an arbitrary number. In this case, I'm looking at sales charts, and I'm making the assumption that the function is ...
0
votes
0answers
15 views

Likelihood function of truncated data

I am having a little trouble understanding the concept and derivation of the likelihood of truncated data. For example, if I want to find the likelihood function based on a sample from a ...
1
vote
0answers
75 views

Significance Tests & Confidence Intervals for Non-normal data

I have 2 nonnormally distributed samples of different sizes (N1~=N2). To evaluate whether there is a significant difference between these samples, I used the Mann_whitney U test (ranksum in MATLAB) ...
1
vote
0answers
23 views

“Sane” quantisation of moderate-dimensional analogue data

Warm-up problem (with solution): Suppose I have a measuring device that spits out a stream of real numbers, which I will model as i.i.d. random variables with range $\mathbb{R}$ and continuous ...
0
votes
1answer
50 views

Large Regression dataset

For a project I need a large regression (least squares) dataset: If $n$ is the number of samples and $p$ the number of features, then I need $p < n$ and $p,n$ both very large. For example ...
1
vote
2answers
79 views

Determining function from simple xy graph

I'm not sure if this question is too vague for here. Will delete if necessary. I have a set of points, (1,782), (2,893), (3,992),... and I'm trying to determine the function that was used to generate ...
1
vote
1answer
70 views

Weird formula for linear regression

I'll try to make the matter as clear as possible given the circumstances. My boss asked me to look at an old report a former employee wrote around a couple of months ago. Apparently the report ...
1
vote
1answer
28 views

Non-close-form Regression Research

As I try to process some physic experiment data that I don't have the closed form formula with unknown parameters, I have to use some regression models like polynomials or normal distributions . The ...
0
votes
1answer
106 views

Hypothesis Testing, simple against composite.

i've got some trouble understanding this exercise from Amemiya's Introduction to statistics: Given the density $f(x) = \frac{1}{\theta}$ from $0 < x < \theta$, and 0 elsewhere, we are to test ...
0
votes
1answer
435 views

Comparing annualised volatility from monthly and annual data

I fear there is a very simple answer to this question and its killing me that I can't see it. I am interested in calculating historical volatility: I have monthly index values starting in Jan 2005 ...
1
vote
0answers
14 views

Isolating clusters in data

This is a problem that I keep encountering in one form or another every so often. Given a large N dimension space with a sufficiently large (M) sample of points. [1] If I were to be asked to find a ...
1
vote
0answers
7 views

grouping of skewed dara

I have a set of data composed of the measurements of spaces. There are 2 distinct sizes represented in this data set. (distinct in that the larger size is larger by some unknown multiple) I am ...
1
vote
1answer
152 views

Mathematical model building with dependent and independent variables

I have been working with data and building models on data. I have developed models in regression using cubic and power series. It works fine for variables with one dependent and one independent ...
0
votes
1answer
30 views

Rescaling Dataset by a constant value

I have two sets of measurements that measure one thing. I would like to graph the relative heights of the measurements, however one set is nearly consistently higher than the other one. I would like ...
0
votes
1answer
49 views

Experimental Data Analysis

Suppose I have performed 2 different experiments to measure the number of cell in a mice. In the first experiment, we measure the cell in odd day (day 5,7,9,11,13) and in the second, we measure the ...
1
vote
0answers
23 views

mutual information for power low distributed data?

I have a dataset with power-low distribution, I would like to measure some kind of correlation/mutual information between the data to its class,(for feature selection task), Can I use ...
2
votes
0answers
165 views

curve fit but unknown function

I face a strange problem. I have data $[X,Y]$ with no noise. If I plot $Y$ as a function of $X$, it looks like a straight line and the regression coefficient is quite good. For the simplest model ...
1
vote
1answer
80 views

Can you please help me model this curve?

I have no idea how to model this curve. Can someone please help?
0
votes
2answers
173 views

A simple GRE data-analysis question - but I dont know what it is asking

It is a GRE data analysis question. I don't if I am dumb in Math, or in English. But I could not understand what is the question a want me to answer. Please give me a hint.
0
votes
1answer
103 views

compering distances between points in different dimension

I have pairs of points, each pair is in the same dimension, and I need to measure the distance between each pair: For example: ...
1
vote
1answer
56 views

Given two arrays, how can one determine the the intersection?

I have two datasets (A & B). They each have 1000 numbers. 99% of the time: A < x <= B However, 1% of the time B < x < A. How can I solve for x, ...
0
votes
0answers
41 views

How to search for an object in more efficient way?

I have a doubt how to check if structure contains an object. Simple sketch of my structure: Root - is a group which can contain groups, keys, values. Group - can contain groups keys, values. Key - ...
4
votes
2answers
177 views

Detecting increasing pulse trains

I have a one dimensional point process representing the times of events which is also mixed in with lots of data that I regard as noise. The interval between the events in the point process are ...
0
votes
1answer
45 views

Type of Distribution for Survey Answers 1 to 10

I'm investigating survey data where participants are asked to answer based on a scale of 1 to 10 typically, the average is around 8.5 with most responses between 7-10, with a lower numbers like 3 ...
1
vote
2answers
211 views

Least squares fit with a trick

Fitting a circle with least squares is easy once you get the trick for $c = r^2 - a^2 -b^2$ and you got a linear set of equations. my problem is as follows: $$z = \alpha x + \beta y + \alpha \beta$$ ...
1
vote
1answer
34 views

How can I mathematically determine the next available index for a child row in this data set?

I have a data set that looks like this: $$ \begin{array}{c|lcr} & 0 & 1 & 2&3&4&5&6&7&8&9 \\ \hline parent & x & x & x & x & ...
1
vote
0answers
281 views

Can you compare data sets with percentages with the Chi Square test?

I’m confused about the Chi Square test.. Apparently you have to use it when comparing frequencies only, but what if both data sets are percentages? e.g. comparing the percentage of smokers in specific ...
0
votes
1answer
28 views

data interpretation

let us consider following picture and question: INCOME: 1. Money from fund raising programmes, 2. Grant from the government, 3. Contributions from individuals, 4. Contributions from corporations, ...
2
votes
1answer
50 views

Optimize database indexes, the sequel

Background For those not familiar with databases. Indices help to speed up database searches, but they come at the cost of memory. Since you like your database to be fast, they are best cached in RAM ...
0
votes
2answers
47 views

Optimize database indexes

Q: I have 14 columns, how many indexes do i need to create to cover all possibilities? Examples of possibilities: col1 col12 col5, col3, col4 col7, col2, col12, col1 all 14 columns -- Order can ...
2
votes
0answers
103 views

The correct probability distribution / way to analyze daily changes

I am working on a report which is being sent through to end users that should flag to them any "large changes" in the day-to-day values for the past 30 days for something we would assume the ...
1
vote
1answer
405 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 ...
2
votes
3answers
158 views

Testing for chaos in data

I have data for 3 variables ,each with respect to the discrete time values. How do I check for the existence of chaos for this 3D discrete system?(I don't have the analytic eqs.,just the data). MY ...
0
votes
1answer
68 views

How to normalize these numbers for better visualization?

My dataset is like this: a1 4565380 a2 676477 a3 359939 ... b1 222431 b2 12222 ... g1 139 ... h1 134 i1 10 j1 11 and goes on.. The problem is when I ...
5
votes
2answers
128 views

Highest points in heart cycle graph

I'm making an application that reads the heart cycle from a device, and I've aimed to get this image: Now, I need to get the highest points that appear in every cycle in order to calculate the ...
1
vote
0answers
39 views

Unit Root Test interpretation

I am analyzing data collected hourly over $9$ years (around $80000$ hours) and I have following result for Unit Root Test : How can I interpret the data? Can I use the Autoregressive model?
3
votes
1answer
21 views

Where can I find a longitudinal study with a binary response?

I've spent the last couple of months trying to find real data (not simulated) of a longitudinal study, but I can't seem to find one. Any topic and time frame is fine, but the dependent variable must ...
3
votes
1answer
134 views

Logistic functions - how to find the growth rate

We have the formule for a model with logistic growth: $$ N_t = N_{t-1} + g\, N_{t-1}\left( 1 -\dfrac{N_{t-1}}{K}\right)$$ where $g$ defines the growth rate and $K$ is the carrying capacity. Let's ...
3
votes
2answers
59 views

Need to find function by the data

I have found interesting sequence, but I can't find its function. Here are the input and output data: ...
2
votes
2answers
60 views

Converting data to a specified range

I am trying to convert data to a particular range of 0-10. Actual Data may vary from - 50000 - 26214400. I have broken this down in to 4 parts as follows - ...
0
votes
1answer
69 views

What is moving window strategy?

I searched on google but I couldn't find appropriate information. I am studying curve fitting and I guess it is related issue. However I don't have any idea about it. Can you explain briefly?
0
votes
1answer
30 views

What is feature selection?

I have been participating in the kaggle digit recognizer competition and after some initial success someone suggested that I look into feature selection. I've done a bit of research but I am having a ...
2
votes
0answers
502 views

Exponent p-value generated in Excel

Excel gave me a p-value of 1.44909E-09 Notice is does not say .09 but 09 This is confusing me, I am trying to analyze my data but am stuck at this point. If it were E-9 it could be ...
1
vote
2answers
57 views

Curve fitting: $a f_1(x)+b f_2(x)+c f_3(x)+d f_4(x)$

I want to fit my data $y$ with a method such as $$a f_1(x)+b f_2(x)+c f_3(x)+d f_4(x)$$ However I don't know how to obtain coefficients $(a,b,c,d)$ of the known functions ...
1
vote
2answers
139 views

Mean and Median Calculations

A group of 20 has a mean = 85 and median = 80. A different group of 30 has a mean = 75 and median = 72. Now, what is the mean of and median for the entire group of 50?
0
votes
1answer
30 views

Quadratic fit check

I've performed LS fit to data in order to fit the following quadratic function: $$f(x,y) = A~x^2 + B~y^2 + C~x~y + D~x+E~y +F$$ Now, I would like to check that the fitted function looks like a ...
0
votes
1answer
97 views

Need help with Lagrange Multipliers in Support Vector Machine

In linear support vector machine with binary classification if we know all the support vectors, geometrically we can create hyperplanes on both sides of the main hyperplane using these support vectors ...
0
votes
0answers
121 views

Normalizing data between 0 and 1

I've got some data that I need to be normalized. I've tried several different ways I've found online, none of them work the way I'd like. I've tried ...
2
votes
1answer
153 views

Techniques to find regression parameters for multiple datasets where a subset of parameters should be the same for all datasets

I have five sets of observations of measured y as some function of measured $x_1, x_2, x_3,\ldots$ and I want to fit five functions to these observations. They have the form $$ y = f(x_1, x_2, ...
4
votes
2answers
7k views

Value range of normalization methods? min-max, z-score, decimal scaling

I am working my way through Normalization (data transformation) of data and was curious about four methods: min-max normalization, 2. z-score, 3. z-score mean absolute deviation, and 4. decimal ...