# All Questions

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### Corresponding SAS mixed model in R [on hold]

I am looking for the corresponding R model for the following SAS model. ...
15 views

### Why not using the R squared to measure forecast accuracy?

Why in literature usually the common accuracy measures like MAD, MSE, RMSE, MAPE ... are used. Why not using the R squared (coefficient of determination)? I was thinking about the difference: By ...
16 views

### lme4 in R: how to specify 2 correlations with random intercept, without adding correlations between random slopes [on hold]

I am trying to specify a model in R's lme4 package in which I have 2 correlations between random intercept and random slopes, but the random slopes are not allowed to correlate. ...
14 views

### Detecting discontinuities in irregularly-spaced data

I am running physics simulations. Sometimes a simulation has insufficient resolution and produces discontinuities in the output variables. These are very easy to spot by eye in a scatterplot. I would ...
9 views

### Are there any open-source implementations of structured prediction methods? [on hold]

I'm currently interested in structured prediction field. I've looked around the web but haven't found any implementations of this kind of algorithms in any of languages. Have I not searched enough or ...
31 views

### Multivariate normal value standardization [on hold]

I am wonder how to standardize multivariate normal value and check that standardization gives correct result. This question is copy of mine from math section where I get no answear or idea about the ...
17 views

### How to calculate test information in computerized adaptive tests

Under Item Response Theory, test information $I(\hat\theta)$ is a function of the examinee's estimated ability $\hat\theta$, discovered a the end of the test, and the items that were answered during ...
16 views

### Is this data really detrended?

I have a time-series vector for a macroeconomic indicator, which clearly has trends, when I apply the detrend method of matlab, I see a change in the ...
24 views

### Interpretation of coefficients in per capita terms [on hold]

I come across an article with a regression output: $y=-53,06+122,58x-200,7x^2$ $y$ is here total spending and $x$ is the ratio of people receiving benefits (of total population). The mean of $x$ ...
10 views

### How to calculate BIC for K-Means to get best K

I'm really new to K-Means clustering technique. I'd like to calculate BIC for K-Means to find best K (number of clusters). I looked around on the web to find a solution in python but there is no ...
18 views

### How can I estimate weibull parameter in R? [on hold]

I'm new user of R. I have quantal response data with sampling test. Before sampling test decide sample size and sampling points. This data is test with '75' sample size and '20'sampling points. ...
8 views

### Computations of Durbin-Watson quantiles

For some educational reasons I am currently trying to re-compute Durbin and Watsons (1951, Paper II) critical values of the lower and upper bounds of their Test-Statistic (dL and dH), and also table ...
27 views

### Find best K value for K-Means clustering [on hold]

I'm doing the K-Means clustering for my data. Following python script does K-Means for 2 clusters. ...
12 views

### Cronbach's alpha internal consistency test for interval scale or ratio scale data with different units

I have recently read dos Santos, S. F. & Brandi, H. S. 2015. Model framework to construct a single aggregate sustainability indicator: an application to the biodiesel supply chain. Clean ...
16 views

### Variables in the regression

Would it be correct if the outcome variable is at the household level, to use variables at both household and household member level as regression explanatory variables? E.g. if the outcome variable ...
12 views

### Relation between P chart and Chi-square test

P chart checks whether a manufacturing process is in control with respect to the proportion of non confirming items and Chi-square test for homogeneity tests whether several populations are similar or ...
11 views

### Normalization in R before doing PCA [on hold]

I have a dataset as a .CSV file (a 70*12 matrix) I've givven it to R as Input data! Now , I want to do PCA on it. But , I should standardize (normalize) it first brfor doing PCA. But I do not know ...
7 views

### Comparing distributions against expected to determine the best fitting

I have a 4 sets of observed absolute frequencies for a categorical variable and the expected frequence for each category (not normal distributions). Would it be correct to use the Chi-square goodness ...
28 views

### Metropolis, simulated annealing and proposal distributions

I'm trying to understand the physical meaning of the proposal step generating function in Metropolis algorithm. In the original paper, and most derivations I found, it seems that it's not much ...
7 views

### marginal effects and total effects in regression with interactions

I have a question that seems very simple and yet I need a final push to lock up the intuition in my head. I am running a regression that can be simplified to look like this: log(wage) = $\beta_0$ + ...
23 views

### How to predict & plot quasipoisson GLM in R

I have a set of complex survey data with sampling weights. I am using the svyglm() function from the survey package in R to ...
20 views

### Duplicate Training Data in Decision Tree Learning Algortihm

I have the following training data set where the first line shows the name of attributes. ...
18 views

### How to calculate distance between 2 lists in r with only general attribute information? [on hold]

I need to calculate distance between two simple lists in R and would like a little logic help please. The issue is that I do not have a data set, rather just a range for each attribute. Here's what I ...
7 views

### Measuring the uncertainty of the average of average rates

Is it possible to determine the mean value of a point by averaging the average rate of ranges that contain that point, and if so, how can the uncertainty of that value be accurately determined? I ...
17 views

### Incorrect class displayed when using 'apply' function in R [on hold]

I see a problem with the apply function in R. 1. This does not show the right class. ...
16 views

### Rules for choosing how much training data one needs to learn a Radial Basis Function model?

I was trying to understand how much data I would need compared to the number of parameters (and to have good generalization) when I train a radial basis function (RBF) network on a regression task ...
10 views

### Blocked Gibbs Sampling using Forward / Backward Algorithm

I am new to machine learning and have been reading about gibbs sampling. From my understanding, gibbs samples a single variable iteratively conditioned on all other variables. In blocked gibbs ...
26 views

### State space model affected from future events?

I understand that a state-space model is a common model where the current observation $y_t$ depends on the current state $x_t$. Is there any common model where the current observation $y_t$ depends ...
12 views

### How to find a linear dependency in a 2-D histogram?

I have a matrix (average of several trials), with x and y as independent variables, and z as dependent variable. It can be plotted as a 2-D histogram. Now I want to detect if there is any significant ...
21 views

### What does the acf of the log of data tell us?

I'm working with time series data. And there is a use of acf ( auto correlation function ) being applied to the log of a ...
19 views

### How find confidence regions for multivariate ( or at least bivariate) distributions other than Normal

I am looking for a method which is able to find confidence regions in multivariate distributions with $(1-\alpha)\%$ probability of occurrence. What I mean by probability of occurrence is that, the ...
16 views

### How to check if two results are consistent

I'm looking at an astronomical object. In one observation, it does something (not relevant what :) 2199 times out of a possible 2936. In another (later) observation, it occurred 2094 times out of a ...
28 views

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### Comparison of Clusters with the Aggregate [on hold]

Just wanted to know if there were any good tests/measures that compare a cluster to the aggregate data. So suppose that I already have clustered/partioned data $x_{i,j}$ (data point j in cluster i). ...
8 views

### K-means or Relative Risk - which method is takes more computation

We are trying to solve a decision around modelling perform for destination grouping. We have a large set of destinations (>500k) selected by a set of guests and would like to cluster them together ...
23 views

### Corresponding RKHS of Common Kernels

A kernel, $k(x_1, x_2)$, has the interesting property that it may be represented as the dot product in a reproducing kernel hilbert space (RKHS), $\phi(x_0)\phi(x_1)$. I know that for the gaussian ...
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### How to plot identical slopes for an ANCOVA (1 categorical variable(2 levels) with 2 covariates) using ggplot2

I am trying to compare and plot regression lines of an ANCOVA when their slopes are the same and no interaction effect There are two sets of ANCOVAs plots that I am trying to create: a) 1 ...