# Questions tagged [data-analysis]

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.

716 questions
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### Different pca plots

I was trying to to learn pca(using the iris dataset) with python and i got some results,so i wanted to test the results ir R to make sure it was good.When i checked the results,it gave me a mirror ...
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### Survey weighting

I took a survey of 142 people, ...
1answer
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### Excel: inverse interpolation

Through Excel I obtained a calibration curve as shown in this figure The equation of this curve is $$y = 0,6209x^5 - 1,7958x^4 + 2,0116x^3 - 1,14x^2 + 0,3584x + 1,33$$ Now, through some ...
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### Using statistics in petroleum engineering [closed]

How can engineers use mathematical statistics to determine relationship between number of wells and oil, gas and water production?
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### Party Invitations Problem [closed]

There is a party on some Sunday next year, it is open to all. a)Everyday at some point, a person comes and drops a slip with contact details in a dropbox. b)A person on a given day could comeback ...
1answer
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### Growth in forward difference

I am looking at a pattern in some data, and I am trying to figure out if it tells me anything about the underlying structure of the dataset, or if this is just an obvious algebraic relationship I am ...
0answers
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### Compare 2 lists and find out their similarity

2 list of data (inventory levels versus order). I want to compare how similar they are. Correlation coefficient can be calculated in Excel as below. The 2 lists doesn’t look similar but Correlation ...
0answers
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### modifying gumbel function to suit data

I have a set of data (x and y), which is right-skewed. I am now looking for a function that fits the data best (least squares). So far I was thinking about a curve that has a form of a gumbel or log ...
2answers
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### Mean, Variance, Standard Variation

I submitted this question the other week to my tutor, but it was wrong. the only thing correct was the mean. He did not tell me why it was wrong or the correct answers. Can anybody tell me why this ...
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### Principal Component Analysis - Why Use Eigenvectors of the covariance matrix?

I've pretty much been trying to learn PCA all day, and I feel like I'm so close. Here are my two main questions right now. Hopefully, someone on this thread can help. First of all, I THINK I ...
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### Probability of failure needed

There are 38 numbers on a wheel. I pick 5 numbers and maintain those 5 numbers for 35 spins of the wheel. What is the probability that 1 of my 5 numbers will NOT be selected within the 35 spins/rounds?...
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### Smooth a variable's trend based on another variable

I have a data with demand (quantity) and price. Their trends follow each other's most of the time. When i plot it, i can see there are times when there is a fallout in the trend. Is it possible to ...
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### Analyzing SATQ scores. Please any tips help.

You are given a data file called Calculus_data.tab(a huge file) We take a random sample of 30 from the data file. The Question: Estimate the difference between SATQ scores for male and female ...
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### Methods to classify observed data into states

Given a time series (that sometimes unpredictably alternates between random and non-random and is not stationary). What mathematical methods are there to classify the observed set of data into ...
0answers
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### Data Transfer - Resolution & Bits

Let's say the 16-bit Unicode representation of characters is transmitted along with its coordinates on a page. If the characters can be freely positioned on the page by having the anchor point of a ...
1answer
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### Data Transfer Speed

If the data transfer to the printer is done pixel by pixel with 3 * 8-bit colors, how long does it take to transfer a DIN A4 color page (21 cm x 29.7 cm) to the printer using the following transfer ...
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36 views

### Decoding confidential numbers expressed as percentages using number theory

This is a actual problem I encountered at work. Little long as it requires some explanation Let $n_1, n_2, \ldots n_k$ be natural numbers and let $s$ be their sum. The expressed as a percentage, the ...
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### Random Walk Modeling - Log Normalization of Data (MATLAB)

Having trouble clarifying which plot correctly log-normalizes the data. 1:steps(i); is a vector of 1 -30 and is equal to the number of steps taken ...
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### Guessing a functional form to use for fitting an exponentially decaying spectrum with peaks

I'm trying to fit an experimental spectrum (Intensity vs frequency) in which the intensity exponentially decays as frequency increases. However, there are peaks amidst the exponentially decaying ...
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### Decomposition of posterior porbability

So, I'm currently working through "Data Analysis: A Bayesian Tutorial 2nd Ed." by D.S. Sivia and I am stuck an equation, which I am not able to reproduce (p.40 - 42 for those who might have a copy). ...
1answer
29 views

### I ran an ANN model and got an extremely low R2 but a pretty good MSE, what does this mean? [closed]

I ran an artificial neuron network on data with about 2,000 rows and 3 features. I got a R2 of .06 which is really low, but a good MSE of .41. Why are these performance evaluators of this model ...
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### Interpolation on curvilinear grid

How could someone interpolate spatial data on a curvilinear grid, like the one in the picture shown?
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### Modeling distributed densities or is it?

Lets say that I am counting pixels over time. Each pixel is either the color red or blue. Let's say that I make up some threshold for the number of red pixels that I count and that when I reach this ...
1answer
25 views

### Understanding the lower and upper limit of a graph

I was recently presented the following graph: I was given very little context and I have to recreate it. I don't want it to be done for me, but some context would help. Any idea what these upper and ...
0answers
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### Problem about multivaluable distributions. (Hotelling distribution)

From $n_1$ p-dimensional random vectors: $X_1,...,X_{n_1}$ independents with $X_i\sim N_p(\mu_1,\Sigma)$ and $n_2$ random vectors with the same dimension: $Y_1,...,Y_{n_2}$ independents with \$Y_i\sim ...
1answer
34 views

### Quantile-Quantile (QQ) Plots

I understand how to assess whether an exponential/normal distribution is suitable to model a piece of data when the parameters are given, i.e. finding the theoretical quantiles and plotting against ...
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### Regression analysis for Measurement values

I'm in a situation where I'm provided with a signal and a couple of measurement values for that signal. Usually the signal will drift a little when the measurement start (i.e. because of heat). I want ...
0answers
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### Minimum and Maximum Data Points in a Spectrum

If I am collecting data that will be used to assemble a spectrum, how often should I take a data point to properly sample, but not oversample given the following information? I can control my data ...
1answer
18 views

### Weighting function for a scatter plot of ratio and difference across several orders of magnitude

I am comparing straight line distances to the shortest discovered path. I have millions of points with a pair (straight line distance,...
0answers
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### Calculating an average of multiple data sets based on priority.

First and foremost I'm no mathematician, it may be a case of over complication. What I'm trying to do is that I have 2 sets of data, I want to calculate one average for both sets but I want the first ...