# All Questions

30 views

### Exact central confidence interval for a correlation

I am working my way through (T.J. Diccio & B. Efron, "Bootstrap Confidence Intervals", Statistical Science, 1996, 11(3), 189–228), and I'm stuck even before I get to the good stuff. In the ...
7 views

### nonlinearTest() in S-plus vs R

Is there any similar function in R does the same thing as nonlinearTest() in S-plus? I am currently working on determine the number of regimes,delayed parameter d and threshold values for the ...
6 views

### VARMAX model in R

Is there a function in R that estimates the VARMAX model? There is one for a VARX (MTS package), but I didn't find one that works with the MA part also...
40 views

### Variance of $\bar x$, simulation with non-iid observations

So I know that the variance of $\bar x$ is usually computed as $\frac{\sigma_x^2}{n}$, and that this assumes the observations are independent. If instead, the observations have some positive serial ...
4 views

### Time in years(x axis) shows years in .5 interval - Time Series using R [migrated]

dsales1156ts<-ts(dsales1156,frequency=365,start=c(2011,6)) # This is my time series created with daily sales data when the first sale day is 6th January 2011. plot(dsales1156ts) The ...
12 views

### Controlling overfitting with random forests for very high dimensional data

I'm using the randomForest package in R to analyse a genetic dataset of ca 100 samples with 10.000 genes. The samples are grouped into 5 classes, the smallest being only of 5 samples. I'm ultimately ...
302 views

### Why does bagging use bootstrap samples?

Bagging is the process of creating N learners on N different bootstrap samples, then taking the mean of their predictions. My question is: Why not use any other type of sampling? Why use bootstrap ...
9 views

### Multigroup Longitudinal Item Response WinBUGS OpenBUGS

I was able to fit the Longitudinal IRT model in Winbugs for an ordinal response by extending the BUGS code I took from the paper by Curtis in JSS http://www.jstatsoft.org/v36/c01/paper/ However, I am ...
23 views

### Using proper scoring rule to determine class membership from logistic regression

I am using logistic regression to predict likelihood of an event occurring. Ultimately, these probabilities are put into a production environment, where we focus as much as possible on hitting our ...
8 views

### Are multi-class techniques for binary classifiers considered ensemble methods by definition?

I am studying ensemble methods which is loosely defined be: Combining models to a make a better model With multi-class techniques such as One-vs-one and ...
21 views

### Neural network and dynamical system

Dynamical systemsare those whose evolution can be described by a rule, evolves with time and is deterministic. In this context can I say that Neural networks have a rule of evolution which is the ...
6 views

### Categorizing text into IPTC subjects

Does anyone know where I can find a corpus I can use to train a classifier into IPTC news categories (http://www.iptc.org/site/NewsCodes/) ? A google search was not very useful. Thank you
13 views

### The variance-covariance matrix of the least squares parameter estimatimation

I'm learning Linear Regression for Regression from "The Elements of Statistical Learning". Why The variance-covariance matrix of the least squares parameter estimates is easily derived( from(3.6) ...
29 views

### How to create a composite of several variables without throwing information away

I want to create an index as a composite of several variables. It was recommend to me to use PCA. However, PCA discards too much information - essentially throwing away several of the variables in ...
5 views

### Constrain regression to correctly rank-order certain cases

I am working on a logistic regression model that attempts to predict the probability that individuals will do a certain activity, where each individual can be described by a number of categorical ...
6 views

### Presenting results of a meta-analysis with multiple moderators?

I wish to present the results of my meta-analysis using the best practices possible. I do not find, however, examples in articles similar to what my output is. Here's a simplification of my model and ...
12 views

### Multiple and long seasonality for a SARIMA model in R

While working on a big data set made of 10-minutes-points of information - i.e. 144 points per day, 1008 per week and ...
11 views

### R geom_smooth: what to write as aes [on hold]

I work with R and ggplot but I'm very new with it. I have already drawn point for 4 different data frames. And now I want to draw 4 regression lines for this points sets. Data frames are packed in ...
15 views

### What is R squared for a neural network and what does it signify?

I calculated R square for my neural network based on a formula I found somewhere, which goes something like: http://i.stack.imgur.com/DojZC.png It should be something around 0.98-0.99. But, when I ...
120 views

### Why not always use ensemble learning?

It seems to me that ensemble learning WILL always give better predictive performance than with just a single learning hypothesis. So, why don't we use them all the time? My guess is because of ...
29 views

### What is this ensemble learning technique called?

For example, I trained two models: one with SVM and one with KNN. Final Prediction = 0.4*KNN + 0.6*SVM Is this considered blending?
15 views

### What model to classify a discretized continuous variable

Consider a variable $y$ (typically, $y_i$ is something like number of inhabitants of city $i$) and some given features $X$. Let us assume that these features are continuous (eg. total city area, ...
9 views

### Obtaining the Psi Weights of a seasonal ARIMA in R

I am trying to quantify the effect of a future random shocks on my seasonal ARIMA model. If I have understood the theory correctly, the easiest way is to express my seasonal ARIMA model in its "random ...
18 views

### Predicting missing values in data [on hold]

I have a dataset that has some missing values. How can I use basic statistics or mathematics to predict the missing values? Right now, I am considering the value before the missing value and the ...
21 views

### Joint distribution of two dependent variables

I was wondering how to (or if it is even possible) find the continuous joint distribution between two random variables $x$ and $y$ when you know the continuous marginal density distributions of both ...
25 views

### Data error in excel- why is 60 displayed as 60.0000000000002? [on hold]

Try this as an example: In cell A1 type 45 In cell A2 type 45.1 Highlight A1 & A2 Drag down until you get the displayed value 60 in cell A151 Click on A151, why has excel changed '60' to ...
4 views

### Fit GAMs with minimum constraints

I have a two-dimensional predictor plane, 0-1-Observations and a priori knowledge of minimal probabilities per combination of the predictors. I would like to fit a model (e.g. GAM from the mgcv ...
32 views

### detect line in scatter

I have repeated samples from the following process: Most samples will only contain points that are randomly distributed on a 2-dimensional plane. Sometimes, however, the sample will contain not only ...
12 views

### how to handle occlusion for face recognition?

If there some occlusion on face (such as sunglasses, mask, scarf), the recognition rate will decrease steeply? How to handle this case? I have do a survey, the PCA reconstruction method have been ...
7 views

### Inner-line correlation (consistency)

In this paper, I found a quite interesting approach concerning measurement of consistency in survey data (provided that each line=case represents a participant). Still, I cannot figure out exactly ...
6 views

### GLMM for SNA and non-independency data

I contact you because my case is particular and I don’t know much about GLMM. I have data of social networks (network metrics) of a nonhuman primate species. These data are by nature non independent ...
9 views

### What is the best test to estimate the correlation between binomial/categorical dataset?

I'm trying to analyze if there are correlations between binomial dataset. I have binomial data (presence/absence) of two variable in different periods and I need to know what is the best way to find ...
8 views

### IT-AIC approach for mixed effects model

I was reading around the Information Theoretic-AIC approach of model selection where AIC values are used to select the candidate set of models. I am quite clear on this. My question is this: for ...
21 views

### Geographic regression

I'm working on a project to estimate real estate and started with some classique techniques, such as linear regression etc. The obtained results are already going in the good direction, but to get ...
33 views

### Beginner question: finding correlations with percentage data

I am trying to work out whether mobile, desktop or tablet users are more likely to perform an action on a site. The data I have is structured as follows: ...
23 views

### Simulate data by using existing dataset

I have a complete dataset with input variables and response variables. I would like to perform a simulation where I give the input variables and generate randomly the response variables. Is there a ...
260 views

### Which is kernel similar gaussian kernel?

I must find a kernel that statisfies as follows: In the my reference paper, the author suggest gaussian kernel that is The purpose of that kernel is that it will take a weight for each points ...
19 views

### Anomaly detection of web browsing sequences

Please consider that I'm quite new to machine learning. I need to create models based on browsing patterns of web users and find deviations from that model. I'm using web server access log files. For ...
26 views

### What do I need in order to draw conclusions from this data?

I have three techniques, called A, B and C. Each can be used independently when trying to perform four related tasks (Tasks 1, 2, 3 and 4). I have run lots of tests, trying all combinations of each ...
80 views

### $E(\frac{1}{1+x^2})$ under a Gaussian

This question is leading on from the following question. http://math.stackexchange.com/questions/360275/e1-1x2-under-a-normal-distribution Basically what is the $E\left(\frac{1}{1+x^2}\right)$ under ...
20 views

### Model Formula with deflator

I'm having difficulties to find the right model formula for my model: $Y_i=a+bX_i$ where Y and X are both deflated by another variable y1/def ~ x1/def + x2/def ...
9 views

### Predicting whether a potential sale will be won or lost

I am currently working on a project using a sales system and trying to come up with a way to use the current pipeline of potential sales to predict the amount of product that will be sold in the ...
23 views

### Spearman's - monotonic? [on hold]

Deas, One assumption for Spearman's correlation is that data have to be monotonic .. I tried to do scatterplot in spss, but I get the following graph that I couldn't decide if it is monotonic .. What ...
22 views

### a question about variance, covariance and correlation [on hold]

Stock A and Stock B have a covariance of 0.87. The correlation between them is 0.03. If the variance of Stock A is 36. what is the variance of Stock B?
29 views

### including interactions in a mixed linear model in R (lme)

I'm trying to test for the effect of soil moisture on transpiration rates. I have plot-level data for 18 plots in 6 different stands of trees (3 plots x 6 stands). I want to treat "stand" as a random ...
35 views

### Non-significant factors after stepwise regression [duplicate]

I have run a stepwise regression on R. However, the summary of the final model includes some factors that are not significant. Why have these factors not been removed? Should I remove these from my ...
27 views

### Basic idea of zero inflated two part models(hurdel) and application to big data (machine learning)

I'm currently working on the data which has 90% 0s in response variable. Based on my research, it seems zero inflated models could be a solution to this. However, while I was reading related ...
6 views

### Assistance with hazard ratios

I want to compare car accident deaths in two groups of people aged 18-24 (lets use this as the reference) and 24-30 after a certain law was changed using a Cox hazard model using SPSS version 22. I ...
This problem appear in an exam put by Chris Sims (3): http://sims.princeton.edu/yftp/emet04/ConfidenceCredibilityEx.pdf Suppose the following model: $y=\beta_1 +\beta_2 X_2+\beta_1 X_3 +\epsilon$ ...