0
votes
0answers
10 views

Increase plot graphic details in R [migrated]

I'm new with R in QGIS, I could write a simple script, and I want to increase the detail of the plot. How can I do that? This is the script: ...
-1
votes
0answers
22 views

Parameter estimation of F-distribution

I have a sequence of numbers, say $x_{1:N_1}$ and $y_{1:N_2}$ which are known to be Gaussian distributed with unknown mean and variance. It is known that the ratio of variance estimates ...
1
vote
0answers
25 views

Different p-values between Wald Z and Wald Chisquare

I have used lme4 for mixed effects models of reaction times and accuracy rates. I could not use lmerTest because the type of model I was using are not yet implemented there (problem with predictors ...
7
votes
5answers
179 views

If two time series $X$ and $Z$ follow $0 \leq Z \leq X$, can we say that $\text{var}(Z) \leq \text{var}(X)$?

Now I see it can't hold. Thank you for the counter examples... You guys rule! Thank you very much for your comments! I added, however, some observations that were missing. Most importantly is the ...
0
votes
0answers
7 views

Multidimensional Scaling - external scale regression using standardized or unstandardized weights

I am having trouble determining whether to use standardized or raw regression weights when using multiple regression to interpret Multidimensional Scaling plots. Different textbooks seem to advocate ...
-4
votes
0answers
15 views

Conduct a hypothesis test of each regression coefficient [on hold]

A regional planner is studying the demographics in a region of a particular state. She has gathered the following data on nine counties. Country Median Income Median Age Coastal A $48,725 ...
1
vote
0answers
13 views

which statistic should I use for inter-rater agreement on nominal data, multiple responses

I have over 400 open-ended responses. The total has been coded by one rater, and a 10% identical sample of the total has been coded by 2 raters. There is a choice of 14 nominal codes, of which the ...
3
votes
3answers
54 views

Endogeneity & IV = model misspecification?

I'd like to raise a controversial point: if you need instrumental variables, your model is wrong. Basic endogeneity problem and the IV solution Let us suppose the basic framework of endogeneity and ...
0
votes
0answers
17 views

R: Fitting a model with periodic, nonlinear and categorical components

Can anyone give me some advice on how to fit a model with linear (some categorical), non-linear and time series components in R? I don't want to use a non-parametric model like a Loess smooth or ...
0
votes
1answer
37 views

Poisson Regression Residuals

I'm modeling the number of doctor visits (a count variable) on factors such as income, chronic condition, insurance, etc. I use the canned Stata command ...
1
vote
1answer
19 views

Feature Selection - Mutual Information with response variable that takes three values

I am trying to calculate Mutual Information scores for Feature Selection. I have successfully implemented the Mutual Information to test each feature against the binary response variable. Each ...
4
votes
3answers
105 views

How to interpret coefficients of $x$ and $x^2$ in same regression

If I have the below functional form for an OLS regression, how do I interpret the $x$ and $x^2$? I cannot interpret them separately, correct? Do I interpret them as a summation of the two ...
-1
votes
0answers
21 views

Extract data from pivot table to data frame (i.e. “reverse the pivot”) [migrated]

I have the following data showing some numbers, broken down by year and month (the more recent happens to be first, but that's not a problem). Is there (in R) a way to easily "reverse the pivot ...
0
votes
1answer
15 views

Decision Trees on training data

Wouldn't any decision tree trained on a training data set have no errors in classification? In other words, wouldn't every data point be classified correctly in the training data set? How would this ...
1
vote
0answers
14 views

Mann-Kendall test STATA

I am new in this forum. I am beginning to work with time series, I have a daily (25,000+ observations) temperature dataset (01/01/1946 - 07/01/2014) I want to test for the following: Trends: So ...
0
votes
0answers
20 views

Misclassification Rate

The misclassfication rate in decision trees is defined as $$1-\max_{j} p_{j}$$ Suppose we want to classify people into republicans and democrats. In the training data, $\hat{p}_1 = 0.7$ (probability ...
-1
votes
0answers
24 views

Hyperplane data points

Would a single data point in the hyperplane (see below) correspond to a single cell in the data matrix or an entire row?
0
votes
1answer
59 views

Orthogonalizing predictors for least squares estimation

I know that orthogonalization in LS is to avoid inverting X'X. The idea behind it is to find variables Z that are orthogonal to each other. Although the process to find those is clear to me, I don't ...
2
votes
3answers
52 views

Similarities and differences between correlation and regression

If I want to investigate how two continuous variables are linked, what is the difference between calculating the correlation coefficient (Pearson's r) versus calculating the (simple linear) regression ...
0
votes
1answer
23 views

Interpretation C value in linear SVM

My C value is very low (close to 0). Does this mean that my feature (dimensions) have no real separative (and thus predictive) value? (As the SVM basically chooses to ignore the training data ...
1
vote
0answers
21 views

Overly-sensitive goodness of fit measure: where did I go wrong?

I'm using the chi-squared goodness-of-fit measure to evaluate instances of a fairly complicated model, but the evaluation is unbelievably sensitive to small variations in the model parameter values. ...
0
votes
0answers
8 views

Inclusion probabilities in a sampling with unequal probabilities with Brewer's method, n > 2

I'm trying to estimate the total of a variable in a population using an unequal probability sample with $n>2$ and the Brewer's selection method. I draw the first unit with probability ...
1
vote
0answers
9 views

Optimal strategy in growing jackpot scenario

There is a betting game, which seems to have "positive sum" situations, and I'd like to find out the optimal strategy. Multiple players place bets against the bank, for and bets that fit winning ...
3
votes
0answers
15 views

Two sample differences between percentage means with negative percentages

Hello to everyone and thank you for all the help you've already unknowingly provided to me in the past. I have a group of percentages around zero that are grouped into two categories, and I wanted to ...
0
votes
1answer
35 views

Neural networks - are local minima bad?

I hear a lot about local minima for neural networks. I understand the theory behind it - but if my neural network finds weights in a local minimum, is that a bad thing? I understand that finding ...
1
vote
0answers
19 views

Predict/impute one cell of matrix using all other cells

The question: I want to predict/impute one missing cell of a matrix using the contents of all other cells. Anyone have ideas on how to do this? The context: The matrix is n people's responses to m ...
0
votes
0answers
8 views

How to model my data into a probit

I am beginning my thesis, and I need some advice. I am trying to estimate a probit model. The binary dependent variable is employment status, and the independent variables include network size, age, ...
0
votes
0answers
5 views

How to interpret factor coefficients regarding unobserved values?

I am presented with a linear regression result that yields the following coefficients: ...
1
vote
1answer
24 views

How to handle unseen features in a Naive Bayes classifier?

I am writing a naive bayes classifier for a text classification problem. I have a bunch of words and an associated label: ...
1
vote
1answer
46 views

Simple SVM Question

For a linear SVM, the documentation tells me the formula is: $$ \frac{1}{2}w^Tw+C\sum\limits_{i=1}^l\xi_i$$ Please explain to me in layman's terms what w (and ξ) represent. Is w the distance to the ...
0
votes
1answer
8 views

Comparing percentages from one sample and between samples

I've conducted a large survey with about 600 responders. Most of the questions were multiple choice questions. I'm interested in comparing several kinds of percentages. First, I'm simply interested ...
0
votes
0answers
24 views

large variables and low sample (p > n) problem: ridge , LASSO, PLS, PCR which is most suitable for predictions

I am trying see whether to go for ridge regression, LASSO or principal component regression (PCR) or Partial Least Squares (PLS) in a situation where there are large number of variables / features (p) ...
0
votes
1answer
25 views

k-means in R generates same number of clusters but different cluster label

Hi there I am running a k-means code in R with the same data and with the same number of clusters, in this case 3, but each time that I run the code, the cluster label changes, for example. In the ...
1
vote
0answers
13 views

Should the 'TPR of adaboost' be better than base classifiers'?

There are two different base classifiers which produce true positive rate (TPR) values 99.46% and 91.79%. When I use these base classifiers in adaboost, what should the new TPR be? Better than two of ...
-1
votes
0answers
14 views

Using a one-way chi-square, determine if the null hypothesis is true, that the parks actually have the same attendance [on hold]

Public Park Families Washington Park 98 Observatory Park 106 City Park 92 Cheesman Park 97 Crestmoor Park ...
0
votes
2answers
43 views

Next steps after obtaining a significant Pearson coefficient

Lets say I have an R value of .5 and therefore an $R^2$ value of .25, and a p value < 0.001. (All through the stock cor.test function in R). Is there a way to isolate those cases/observations ...
2
votes
1answer
26 views

Multi-armed bandit in face of full reward information

I am new to this area of machine learning. I am just walking myself through UCB1 algorithm which seems to assume that the payoff can be learnt only for action that ...
-1
votes
0answers
15 views

values for categories [on hold]

Appreciate if you can help me with the following. I have created categories High, medium and low and I need to transform them in ordinal numbers for further calculation. What is the best approach to ...
2
votes
1answer
44 views

Optimal Allocation

A campus population of size N=9000 is to be surveyed by a stratified sample for the prevalence of a certain disease based upon three strata of respective sizes $N_h$ = 1000, 3000, and 5000 for h = 1, ...
0
votes
0answers
19 views

Constant RMSE margin between training and teseting set

I have a large number of independent datasets of varying size but same feature meaning. Features and outcome are both binary. I am trying to fit logistic regression to the data. I estimate ...
1
vote
2answers
88 views

Hat matrix,$H=X(X^{\prime}X )^{-1}X^{\prime}$

What is the importance of hat matrix, $H=X(X^{\prime}X )^{-1}X^{\prime}$ in regression analysis? Is it only for easier calculation ?
1
vote
1answer
36 views

How does cross-validation and the Bayesian method overcome the overfitting problem?

I was told that cross-validation and the Bayesian method can overcome the overfitting problem. I was told that comparison of models in a Bayesian way is actually doing cross-validation... What is the ...
3
votes
1answer
19 views

Equivalent of paired $t$-test for dispersion

I'd like to compare, in a within subject design, the dispersion of two conditions. At first I thought about taking the standard deviation by individual and condition, and compute a paired $t$-test on ...
0
votes
1answer
28 views

Getting all zero correlations,$\rho_{ij}=\frac{\mathbb cov(e_i,e_j)}{(V(e_i)V(e_j))^{1/2}}$

Consider the general regression model $$Y=X\beta+\epsilon$$ where, $Y$ is an $(n\times 1)$ vector of observations, $X$ is an $(n\times p)$ matrix of known form, $\beta$ is a $(p\times 1)$ vector ...
0
votes
0answers
16 views

Random effects models / Integrate over the random effect

I am trying to do maximum likelihood estimation and trying to see if the problem can be formulated using a random effect model. Here is the problem description: There are $100$ pairs $(N_i, D_i)$ ...
0
votes
1answer
36 views

Clustering of items based on their category belonging

I am trying to find a clustering algorithm, but I'm working with already classified items. Basically, items belongs to one or more category, which are already known. Categories are absolutely not ...
0
votes
0answers
12 views

Advanced R Programming Questions. Variable Names in Environments [migrated]

I wrote 2 functions to archive objects from R (with their names - that's really important for me) and, if an object is of class lm, to archive data used to conduct ...
1
vote
0answers
21 views

Proper scoring rules for observations with different supports

Suppose to have a bivariate variable $z_t=(x_t, y_t)$ indexed by $t=1,2, ..., T$. Suppose now that the two components have different support, i.e. in my specific problem $x_t \in \mathcal{S}$, where ...
0
votes
0answers
21 views

Forecasting time series with missing data and irregular intervals

I have a data set of medical drug stock levels at health centres and I want to forecast monthly consumption over the following 3-6 months. However about 30%-40% of the data is missing and some of the ...
-2
votes
0answers
18 views

Calculation of root mean square error [on hold]

How can I calculate root mean square error (RMSE) from a set of wind speed data ? An example would be great!

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