# All Questions

20 views

### What type of statistical analysis would be best to use?

I'm awful at statistics so could really use some help regarding statistical analysis and which approach to use. Here is what I know - I need to determine, based on stats I have been given, whether ...
21 views

### Error in R's pbeta function with log=TRUE. Why could it be? [on hold]

R's function pbeta is supposed to calculate the incomplete regularized Beta function. If the flag log=TRUE is passed as an ...
7 views

### Dependence Modelling with Copula

I am referring to the book 'Dependence MOdelling with Copulas by Harry Joe. The book has a website that demonstrates the programs used in the book. It refers to a library called CopulaMOdel. However, ...
9 views

### Using predictive algorithms for descriptive purposes? Correct? Any resources?

Newbie here. I've been learning lots of predictive modeling with R/python using the well-known algorithms: decision trees, random forests, SVM, logistic/linear regression, k-Means, k-NN. But I'm new ...
20 views

### Quantile regression by hand (without a package)

I want calculate a quantile regression for homework by hand, without a package. What is the process?
10 views

### How to fit an logistical autoregression in R?

I modeled the relationship of $X$ and $Y$ by the logistic function. The residual plot displays autocorrelation which I'd like to rid. I want to try adding trend component to $X$, thus the model ...
10 views

### find weights of different methods

This question is a little general, but I am looking for suggestions of a method. I have several images that contain images of animals and I have to characterize which animals they are, let's call them ...
143 views

### What is a multivariate random variable?

I've been trying to read the Wikipedia article on multivariate random variables but I'm having trouble getting past the math. Is there a more intuitive explanation? I'm assuming that a univariate ...
23 views

### linear regression - what tests will support my results?

I have collected data about daily bitcoin returns to the US-Dollar and calculated an online sentiment value with data from a social media platform. I further made a linear regression on that data ...
19 views

### Logistic regression (multinomial)

Having trouble getting my head around this. I should mention, I am not a staistician and all my 'knowledge' is self taught. I am trying to compare 4 hospital sites for patient outcome (either ...
15 views

### Determining statistical significance of data changing over time

I have collected motion data from three people over two days. Each of the subjects collected motion data from themselves for around 5 hours a day, for the two days, so I have about 10 hours of data in ...
19 views

### Can we write the likelihood of a GLM in generality?

So I know we can explicitly write down the likelihood of any specified GLM model, for example the likelihood for the logistic regression model would be ...
16 views

### Results change when variables are scaled [on hold]

I am analysing nested data using LME4 and find that my results (significance) change depending on whether variables are scaled or not!? ...
10 views

### Distribution of the duration of a markov-process in a specified state during a specified time

I have a continuous time markov chain with two states $A$ and $B$. The transition rate $A\rightarrow B$ is $\lambda$ and $B\rightarrow A$ is $\mu$. Imagine that $P(X{t_0}=A)=1$ (the process starts in ...
21 views

### Clustering from similarity/distance matrix

I have a symmetric and weighted adjacency matrix with $n$ elements. What algorithms exist to cluster the elements from this matrix? The matrix has values between $0$ and $1$. In the case of a ...
29 views

### ttest or wilcoxon

for a user study I want to compare some tasks. Each tasks has 2 conditions on a intervall scale. From each task I want to test the the conditions with: a t-test if both samples are on a normal ...
46 views

### How to interpret this interaction in R?

How would you interpret this interaction? The structure of the data is all integer variables. Inc.fix= income, age.fix=age, profit99= profit ...
14 views

### Convert principal components based on covariance into principal components based on correlation

I am wondering if there is any way to mathematically express the change in direction of the principal components from the $2\times2$ covariance matrix to the correlation matrix. In other words, if ...
36 views

### How I can interpret mean, and standard deviation

have a sample of 30 data for daily energy consuming of a person. I found the "Mean" and "Std.Dev." of my samples as follow' Mean = 150 Std. Dev.= 30 I want to prove that he/she has a stable energy ...
11 views

### how to improve linear regression model [on hold]

i am working on a simple linear regression model for practicing in order to learn machine learning . my model runs correctly however it get a bad score which means it is a bad model so any advice for ...
22 views

### Quasi-Newton Accelerator (QN1) for EM Algorithm

I am trying to implement what is called a "very simple to implement" accelerator for the EM algorithm. Specifically I am talking about the QN1 algorithm, described here, and am using a multivariate ...
7 views

### Difference estimation VS estimation of the mean [on hold]

What is difference estimation? How does difference estimation differ from estimation of the mean?
12 views

### Single value decomposition applied to Lee Carter in R

I have a problem regarding the svd in R. It is applied to matrix m, 101 rows by 69 columns, which is the demeaned log mortality rates. When I apply svd(m) (I left nv and nu out), I get d which is a ...
15 views

### What is the chance level accuracy in unbalanced classification problems?

Suppose one has a balanced classification problem (50% of 0's and 50% of 1's). In such a case, the so called chance-level accuracy of classifier would be 50%. What is the chance-level accuracy if the ...
14 views

### R: plotting decision tree with leaves text labels [on hold]

I use a package mvpart (MS -species in sites, TTE - parametres of environment) ...
7 views

### Find correlation between two populations [on hold]

I am working on my dissertation and I have to find out the correlation between two populations on the basis on certain data. I have the data in numerical format too but I am finding it hard to come to ...
11 views

### Regression with caret and uknown levels [on hold]

I'm trying to perform a cross-validated linear regression with caret. Unfortunately it always fails as some values for levels are not to common and therefore the prediction fails with the error ...
12 views

### Need better guesses for nls [on hold]

I got need better guesses for this nls function, I was wondering if anyone could help me find better guesses. Sorry I don't know how to post code correctly, everything below here is code. ...
15 views

### Detect rhymes in lyrics

I am testing several features computed from a dataset with several machine learning algorithms, and I would like to see if rhymes contribute to the genre classification of lyrics. Therefore, I would ...
29 views

### Rules for selecting convolutional neural network parameters

Are there any good papers that cover some methodical ways of picking dimensions of filters and pooling units as well as the number of convolutional layers?
23 views

### Structural Equation Modeling in R throws an error: system is computationally singular [on hold]

I am using Structural Equation Modeling in R. Below is the model that I have specified. The error that I am getting while training the model is: system is computationally singular: reciprocal ...
36 views

### Similarities and dissimilarities in classical multidimensional scaling

I am having trouble reconciling between several terms in MDS. According to [1], Section 14.8, Classical MDS takes similarities as inputs. In [2], also cited in Wikipedia, Classical MDS takes ...
29 views

### How to interpret my coeff/ORs when the main effect of my two predictors is significant but not the interaction between the two?

Apologies as this has been posted before in similar topics but still I am trying to stretch my brain to understand it. I have panel data, I am looking at both binary and count variables as outcomes ...
18 views

### incremental quantile regression

I am reading about quantile regression. I wonder if there is a way to incorporate new data into the regression model and update the parameters on the fly. [1] seems to propose a similar idea, however, ...
6 views

### Why are sampled generated by a Circular Block Bootstrap non-stationary

Generally, samples produced by block bootstrap methods do not produce stationary series, even if the original data generating process is stationary. I can see why a moving block bootstrap or ...
32 views

### Cramer's $\phi$ for three-way contingency tables

Can Cramer's $\phi$ be determined for three-way contingency tables? I know how to calculate the expected values, chi squared, and how Cramer's $\phi$ works with two-way contingency tables. However, ...
8 views

### Why do clustering internal validation indices are decreasing with the number of clusters?

I get the same pattern for 3 different indices: Silhouettes, Dunn and Connectivity- as the number of clusters increases, the score decreases. I am using several clustering methods and several distance ...
15 views

### What does “10-fold cross validation” mean when only a training set is provided? [duplicate]

Recently I encounter "10 cross validation" several times in literature reading as well as using a data mining tool "Weka". I checked wikipedia, it states "One round of cross-validation involves ...
8 views

### How to calculate non centrality parameter?

Suppose $Y\sim N_p(\mu,\sigma^2I_p)$. Let $A$ be a symmetric idempotent matrix. I want to show $Y^{T}AY$ follows a chi-sq distribution with some non centrality parameter. Suppose ...
9 views

### How to calculate dissimilarity function between two clusters?

I want to write my own code for Dunn's index. If P is dissimilarity measure,then P(min) is fully determined by the pair(x,y) of most closest vectors.(Pattern recognition,Theodoridis & ...
35 views

### Differences between log-log, semi-log and linear regression

Can somebody please explain the differences between using the in the linear/semi-log/log form and also pros and cons of each other.
22 views

### Reducing number of variables for Independent Component Analysis

Say I have a dataset with $n$ observations of $p$ random variables. Since $p$ is "large" (mine is 72), I would like to perform a fastICA only on a subset of $k$ variables, maintaining the same number ...
5 views

### Gini index on data with error margins

I have data series and I want to calculate Gini coefficients for each row as an estimate of matrix sparsity. Hoever values contained in the rows are not exact and have error bounds. My question is ...
15 views

### How to create a realistic distribution of cities? [migrated]

I'm not sure if this is the right community to ask this, so let me know if it's not. I'm wondering if there's been some empirical research as to how villages and cities are distributed around other ...
6 views

### Interpreting the Cowan Generalized Sign Test formula

I'm working on a finance project where I have to calculate a number of statistics related to abnormal returns surrounding an event. One of the tests I'm doing is the Cowan Generalized Sign Test, ...
18 views

### Testing significant difference of correlation matrices

I'm interested in exploring whether responses to a series of attitudinal questions differ across various countries. I could check significant difference in mean scores but am more interested in the ...
23 views

### Compare lists of genes

I have two lists of differentially expressed genes: the list 1 was derived from the universe A of total genes while the list 2 was derived from the universe B of total genes. A number of genes is in ...
17 views

### Model comparison vs. running a model

I recently ran into a puzzle when doing two different types of analyses, and I was wondering if I could get your thoughts on it. In a nutshell, my experiment manipulated two factors in a 2 x 2 ...