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

2
votes
0answers
161 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
167 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
97 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
176 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
44 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
210 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
277 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
102 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
377 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
155 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
67 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
124 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
67 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
450 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
55 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
126 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
94 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
144 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 ...
1
vote
0answers
97 views

Least squares fit or decomposition of average points (from data)

I have a set of data consisting of the averages of a function $g(r)$ at regular intervals; i.e. my first datapoint is the average of the function from $0$ to $\Delta r$, the second point is the ...
2
votes
1answer
201 views

Kalman filter for acceleremoter and gyro

I have read a lot of literature on this topic, but many questions still remain. (Many formulae are here below, so, who prefers to look at them in a more comfortable manner can find a MathCAD sheet ...
2
votes
1answer
184 views

Lloyd's algorithm in normed vector spaces

How do I run Lloyd's algorithm in a normed vector space? The space: L*a*b* color space, finite sRGB segment, $R^3$ The distance metric: CIE94 using L*C*h* information derived from the L*a*b* ...
1
vote
3answers
4k views

Find the median given a table of relative frequencies

I came across the following GRE question. I had no problem finding the mean. However, the answer for the median is given to be 1. I don't understand how they arrive at this. Find the mean and ...
0
votes
1answer
29 views

Rate of Growth of pyramid structure.

This might be simpler than I'm making it out to be, but how can the growth rate of the pyramid structure be represented. ...
0
votes
2answers
72 views

Numerical integration of a derivative dataset

I have an experimentally measured derivative data ($\frac {dy}{dx}$) at a range of times i.e $\frac {dy}{dx}$ for $0 \le t \le tf$. Integrating for $t=0$ is fine, since $y(x,0)$ is known. However, ...
1
vote
0answers
48 views

How to understand the task about bootstrap?

I have the following task. Let $X_1,\ldots,X_n$ be a sample (i.i.d.), $T_n = \overline{X}_n^2=\left(\sum\limits_{i=1}^nX_i\right)^2,$ and $\hat\alpha_k ...
0
votes
0answers
173 views

Choose a right optimization method

I have a question related to optimization method selection. Suppose now I have some observation data (1D) as well as the underlying function model. For example, I use the following codes to generate ...
0
votes
1answer
206 views

How to determine a function from outputs

Given the following inputs and outputs to a function, how would I determine an algorithm to fit? ...
1
vote
1answer
274 views

Normalize data with large spread in values.

I'm currently trying to rank a set of data. The issue is that my initial rank comes from a search on google and the returning result set. The spread in values is ranging from 33 all the way up ...
1
vote
0answers
39 views

problem in dimensionality reduction

I am using multidimensional scaling to plot my data in R. However there is a hierarchy in my dataset which i want to exploit and I am using the delaunay triangulation to visualize the plot. So now I ...
1
vote
1answer
173 views

Mathematical calculation to regenerate numeric series

I am searching for a mathematical technique by which I can perform the following, Let me explain first what i want to do. consider a numeric series: ...
1
vote
2answers
5k views

Use a set of data points from a graph to find a derivative

I have a data logger that is recording the temperature readings from thermocouples at a specific interval. This gives me data points that I can graph where the x-coordinate is time and the ...
0
votes
1answer
126 views

Dividing data of a given distribution

Having a dataset with distribution $p$ (e.g. uniform or normal), if we divide the dataset into $n$ parts with equal size, is it valid to say that each part still has distribution $p$?
0
votes
1answer
105 views

noisy 1-second GPS data [closed]

So, I come from a programming background, but not a mathematical one. I have a problem that I'm sure has a great mathematical solution! so, I have GPS data points for every second of a drive a car ...
1
vote
1answer
47 views

Box Plot Log Scaled?

When making box plots to represent data, is it logical to set our axis scale to logarithmic? Or does that defeat the whole point of a box plot?