# All Questions

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### Cran Package from Google for Forecasting multivariate time series [on hold]

Recently, i saw the package that can forecasting multivariate time series and evaluate the effects of variables like promotion at main time series. Please help me to find it again
21 views

### How to use delta method for standard errors of marginal effects?

I am interested in better understanding the delta method for approximating the standard errors of the average marginal effects of a regression model that includes an interaction term. I've looked at ...
14 views

### Naive ElasticNet in the glmnet package

In the R package glmnet, does it calculate the Naive form of ElasticNet or is the output rescaled with the term (1 + lambda)?
23 views

I'm trying to solve a stats problem as outlined below; I'm a bit new, however, and I'm not sure how I could solve this problem. Assume someone has lost their keys, and uses an inefficient random walk ...
62 views

### Unified view on shrinkage: what is the relation (if any) between Stein's paradox, ridge regression, and random effects in mixed models?

Consider the following three phenomena. Stein's paradox: given some data from multivariate normal distribution in $\mathbb R^n, \: n\ge 3$, sample mean is not a very good estimator of the true mean. ...
23 views

### Relationship between Gini Importance and Prediction Performance (say AUC)?

I want to use the decrease in Gini impurity to rank features for my random forest classifier. I understand that the decrease in Gini impurity at one node is calculated as:  \Delta i(n) = i(n) - ...
12 views

### Assessing predictor contribution to model output

Many of machine learning methods are considered as "black boxes". Examples of such methods are SVM, Neural Networks, Random forests etc. One may apply sensitivity analysis techniques (as described for ...
26 views

### How to determine if GLM quadratic term should be set up orthogonal or non-orthogonal

I am setting up a GLM in R where I have only one predictor variable and its quadratic form. I understand that in R I have 2 options. ...
60 views

### How can I remove multicollinearity from my logistic regression model?

I am working on Sales data. i have binary variable win/loss the opportunities and rest are the activities done by sales force (sales guys) with 40+ variables (different types of activities done for ...
24 views

### Generating two normally joint distributed Random Variables

If I generated two random variables with mean $\mu_1$ and $\mu_2$, but use the covariance matrix as the second parameter of the normal distribution - does this imply that the two variables are jointly ...
7 views

I have three time point data of my intervention study(pre-test, post-test and follow-up test,0, 2.5 month and 3.5 month from initial data). I am confused with slope loading how to load this value. I ...
8 views

### Scoring outputs from multiple decision trees

What is the best way to score outputs of multiple decision trees that classify instances of different classes? Say I have two decision trees. One tries to classify instances to class A, another one ...
13 views

### connecting 2 columns into 1 + change to numeric not working [on hold]

I am trying to run some R code for loading data from files and than do some trails with pair trading. this is my code: ...
21 views

### Why does the null deviance in glm.nb differ between models of the same response variable?

I'm struggeling to understand the topic of deviance. Let's have two models as follows: ...
18 views

### Baum Welch and a 1 state Markov model?

I'm using the Baum-Welch algorithm to determine the parameters of a 2 state Hidden Markov Model. It determines fairly well. When I increase the sample size, the estimations get more concentrated, and ...
28 views

### How to analyze elastic net fitted model coefficients

SOLVED: an elastic net model, as any other logistic regression model, will not generate more coefficients than input variables. Check Zach's answer to understand how from an (apparent) low number of ...
216 views

### Analyze scatter plot

I want to study the relationship between two variables. I've got the following scatter plot. But now I'm hesitating on what to do with this: Should I check the assumptions of OLS and then use the ...
14 views

### R: Analyze scatter plot [duplicate]

I want to study the relationship between twe variables. I've got the following scatter plot. But now I'm hesitating on what to do with this: 1) Should I check the assumptions of OLS and then use ...
22 views

### Stratified sampling for creating test/training sets when there are continous and categorical variables to consider?

Assume a simple clinical study with N=200. Half of the participants are men and half of the participants are women. The hemoglobin of the participants ranges between 80 and 150. There's also several ...
26 views

### What is the difference between Bézier splines and Loess curves?

I'm a bit naive on this topic, and wanted to understand the difference in the mechanics of Bézier splines and Loess curves as curve-fitting methods.
40 views

### More flexible bell shape than log normal distribution

I am looking for a very flexible bell shape function, with asymmetry on both sides of the bell, also with the possibility that the left arm of the bell had a milder slope while the right had a steep ...
37 views

### How to get a posterior distribution from Gamma and Binomial distributions [on hold]

I am investigating the time on book (t) before write off.The sample data consists of times taken until write off, however these times have been calculated from accounts that have been written off ...
23 views

### Determine where hazards starts to increase for a continuous variable

I'm interested in a continuous variable, namely blood pressure. The higher the blood pressure, the greater the risk of heart attack and stroke. However, observational data frequently report that also ...
29 views

### Changing reference level/re-leveling contrasts changes results in non-convergence

I have a question regarding re-leveling in lme4 1.1-7. Experimental Design: Our experiment is an eyetracking while reading study (single sentence stimuli). We are analyzing four different ...
5 views

### Why high variance noise change the direction of eigen vector? [duplicate]

Why eigen vector turns towards direction of maximum variance?.I have observed that classical PCA fails in presence of outliers.Can u explain
32 views

### is the sum of a poisson process a poisson process?

I would like to write an application that emits events distributed by a Poisson process with some $\lambda$ I need to separate the generation of these events in multiple processes, but I only have a ...
21 views

### Is there a way to measure overlapping between two clusters? [on hold]

Is there a way to measure overlapping between two clusters that underlie the data? If there is, can any clustering techniques can measure the overlapping? I am not sure I understand it correctly.
19 views

### ARIMA model in R vs S+ [on hold]

I want to use ARIMA model. I use both S+ and R but I don't know which is better. What are your suggestions on using R or S+ package for time series analysis and ARIMA model?
39 views

### Randomly constructing a probability distribution for simulation

For a simulation, I want to construct the probability distribution of a random variable $X_k$ that takes only finite number of values $x_1, \cdots, x_N$. I have to assign values to each probability: ...
25 views

### What are the pros and cons of using median imputation to handle missing value?

I have to choose between median or mean imputation to handle missing values. I feel median imputation will work better because it is a number that is already present in the data set and is less ...
32 views

### Clustering methods for decision trees

My thesis work examines e-commerce data that is clustered using a decision tree, but I am uncertain about where to start. What algorithm or methods does one use to do this?
8 views

### selecting genes specific/agnostic to condition

I have a microarray transcriptomics experiment. The design of which is something like this : ...
33 views

### Extracting slopes for cases from a mixed effects model (lme4)

I would like to extract the slopes for each individual in a mixed effect model, as outlined in the following paragraph Mixed effects models were used to characterize individual paths of change in ...
19 views

### Do deep belief networks minimize required domain expertise, pre-preprocessing, and selection of features?

I'm trying to get a basic layman's grasp of deep belief networks and deep learning in general. I've read a few papers and watched a few presentations, but there's one aspect I'm hoping someone can ...
15 views

### Calculating euclidian distace among z-score values

First of all I should say I'm from a biological domain. I'm trying to cluster web visitors based on the time they spent on each web page. Let's suppose my raw data set is in the following ...
17 views

### Is there an R package to calculate differential entropy

I am trying to calculate differential entropy over my data. This is how a subset of my data set looks like :- ...
12 views

### Categorical Variables - Factor Reduction - Can I use the dependent variable?

I am working on a basic fraud detection model. I have about 10 independent features and I am trying to predict if a given transaction is genuine or fraud. Most of the features are categorical and each ...
4 views

### In R, how to create contour plot where lines indicate elevation and color indicate magnitude of a separate value? [migrated]

My specific example: I have a dataframe, say 'df', containing columns of x coordinates, y coordinates, elevation, and I have a vector of precipitation values associated with the x/y coordinates (say ...
20 views

### How to account for endogenous program placement?

When we do the standard difference in difference to find the causal impact of a policy, do we assume that the assignment to treatment and control groups was random? In other words, if my program was ...
33 views

### Confidence intervals for median

I have a distribution of samples with a small number of values in each one (less than $10$). I have calculated the median for each sample, which I want to compare with a model and obtain the ...
33 views

### I did this problem but I got percents as the answer not two values. What did I do wrong?

Suppose that the lifetime of a particular electronic circuit has a normal distribution with mean of 50,000 hours and a standard deviation of 8,000 hours. You select a random sample of 25 circuits 1) ...
11 views

### 75% success, ranges for given sample sizes with 95% confidence

A given task has a 75% chance of success. With 90% confidence, what would be expected ranges of success for - 10 attempts - 50 attempts - 100 attempts - 1,000 attempts - 10,000 attempts very many ...
50 views

### Predictive with uniform likelihood

I'm trying to get a predictive density and currently getting something which I know can't be true (based on both logic and simulation based techniques. Here's the relevant information. $\theta$ is a ...
11 views

### What may prevent you from implementing WLS [on hold]

here's the model: respond = B0 + B1resplast + B2avggift + B3propresp + B4mailsyear + u Please correct me if I've done this wrong, but here's what I have so far: QUESTION 1: find the expression for ...
11 views

### is my sample representative of the population

I have a set of responses from a survey I have conducted. I would like to see if a sub-sample of the respondents are representative of the entire respondents that have responded to the survey. I don't ...
28 views

### Can anyone provide a peer reviewed reference for the calculation of least squares means as implemented in the R package lsmeans?

I am using the lsmeans package from the R programming language for follow up analyses of a linear mixed model. However, my target journal does not generally use these methods and I would like to have ...
15 views

### elastic net- confidence intervals for parameters

Can I see the intervals and p values for each coefficient in elastic net model? I wrote: ...
15 views

### Using variance from a Jeffreys prior in a Prevalence meta-analysis

I am doing a meta-analysis on a group of studies, where the observation is a rate (no. of successes / no of trials). Some of the studies have small sample sizes (n<10) and/or did not observe any ...