0
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0answers
1 views

algorithm Matlab function 'stream2' and 'stream3' use to compute streamline

Can anyone explain how the MATLAB functions: stream2(x,y,z,u,v,startx,starty) and stream3(x,y,z,u,v,startx,starty) compute stream lines from vector data u and v? In the stream2.m file, it calls the ...
1
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0answers
6 views

Reference for dimension reduction techniques

This is a follow-up question to Is PCA appropriate for comparing subsets of panel data?. It turns out that, yes, PCA is appropriate. But there are also many other ways to reduce n-dimensional data to ...
0
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0answers
7 views

Non-significant ANOVA but significant pairwise comparisons: how is it possible?

When I do a 2 (tasktype: slogan vs. product) x 2 (novelty: old vs. new) ANOVA, the interaction and the main effects do not seem to be significant. But when I look at the pairwise comparisons, I see ...
0
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0answers
5 views

Time delay embedding

TIme delay embedding theorum given by Takens says that from a time series of a single variable $x(t)$ we can contruct multiple vectors and is given by the formula $X(t_i) = [x(t_i),x(t_i+ ...
0
votes
0answers
3 views

Brewer's method for sampling with unequal probabilities with n>2

I'm trying to use Brewer's method to sample 12 units out of a population of 73. I read on Brewer and Hanif's "Sampling with unequal probabilities" that the probability must be proportional to ...
0
votes
1answer
8 views

Plotting a Gaussian in python

so I am trying to plot a histogram of my data and I seem to be a little confused here. I am using matplotlib in python. Here is the code from their website: ...
1
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2answers
7 views

How do I compare sample means in this experimental-control group study?

I am hoping to compare the sample mean of an experimental group to the sample mean of three control groups. Here is some context for the study: The experimental group consists of ~60 persons with a ...
0
votes
1answer
12 views

An exact paired perm.test is returning a p-value of 0 for large sample sizes

I'm trying to find the p-value from an exact paired permutation test. For small samples it works fine: ...
4
votes
0answers
19 views

Follow-up question: When should you center your data & when should you standardize?

I have a follow up question to MånsT's reply to the "When should you center your data & when should you standardize"-question. ( I cannot leave a comment as I am below the magic "50 reputation".) ...
0
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0answers
12 views

Combine probability distributions defined on different domains

I have a beta pert distribution of wall heights, with minimum 0.4m, and maximum of 1m. I also know that along any wall I have either a normal distribution of openings (they are mostly in the middle ...
1
vote
0answers
8 views

Confidence interval for a constrained fit to Gaussian-like data

I'm working with data from an instrument which is expected a priori to produce Gaussian (normally) distributed data: \begin{equation} G = A\exp\left(-\dfrac{(x - \mu)^2}{\sigma} \right) ...
2
votes
1answer
30 views

Logistic regression & categorical explanatory variables

I'd like to perform logistic regression with some categorical explanatory variables with more categories than just binary 0/1. Is this possible and why? I am inclined to think that this would give ...
0
votes
0answers
7 views

slope of non linear noisy data

I have data from{ Erne /Soho} for time in unit( hour )on x-axis and the intensity in unit ( 1/s.sr.cm2.Mev/n) on y axis the data so long from 1500 points to 2500 points and ...
1
vote
0answers
11 views

Classical or robust variogram for incorporation into generalized linear model

I'm modeling counts of organisms over time at eleven locations. I'd like to account for temporal autocorrelation in the counts, assuming it's present. As the data are not equally spaced in time, ...
1
vote
1answer
20 views

Interpreting the logit results in terms of dollars

If we regress the choice on some cost variables, then how would you interpret the meaning of the coefficients? In this paper published in American Economic Review, link: ...
0
votes
1answer
11 views

What statistical method to correct systematic error in the output of a economic optimization model?

I am working with an economic optimization model which attempts to model the dynamics of a certain commodity market (prices, quantities, production etc.) for different frequencies (monthly, quarterly, ...
0
votes
1answer
12 views

R Error in chol.default(A) krigeST from gstat package

I am working with an hourly dataset of air temperature, recorded at ~200 stations over a relatively small area. I chose a space-time variogram (e.g. sum-metric) to fit my data and am now trying to ...
0
votes
0answers
17 views

Multinomial logistic regression interpretation in R

I have run a multinomial logistic regression test for the interaction between species of deer, days a camera trap was in the field and type of reaction. The model with the best AIC value was: ...
1
vote
1answer
24 views

Monte Carlo computation of expectation when there is dirac delta

Let $Z \sim N(0,1)$ and let $Y=Z$. Suppose I wish to perform the following weird computation: $f(z)=\int f(z|y)f(y)dy=E_Y[f(z|y)]$ and then use Monte Carlo to estimate $E_Y[f(z|y)]$. The problem is ...
1
vote
1answer
11 views

How a quota sample should be executed?

Let's say I have a population stratified by gender and age group. Having their proportions, how should I choose the sampling units for interview? How do I ensure the defined quotas are met? If the ...
1
vote
0answers
9 views

How to specify binomial glmm with random and correlation in R?

I am working on developing a model with a binomial response variable. My data consist of GPS points from tracked animals. The data set is large and contains 15,000 observations from 40 individuals. I ...
0
votes
1answer
19 views

Random Forest Usage

Random Forest Usage: I have run random forest in R. It gave me confusion matrix and variable importance. Variable importance can be used to rank importance of variables in the model. My question is ...
0
votes
1answer
19 views

Weakly informative priors for “r.v. $\mathbf{x}$ is not close to $\mathbf{x}_0$”?

Given some fixed vector $\mathbf{x}_0\in\mathbb{R}^d$, I want to put a prior on a random variable $\mathbf{x}\in\mathbb{R}^d$ so that "it's not very close to $\mathbf{x}_0$". For the moment I put a ...
2
votes
1answer
22 views

Convert normal pdf into lognormal pdf

I have fitted a mixture of 3 normal distributions to my log-transformed data Y, as the package I'm using cannot fit a mixture of lognormal distributions. My questions is: how I can convert pdf from 3 ...
0
votes
0answers
20 views

Compute similarity $\max(\max(\cdot))$

I have the following table where every column is composed of $4$ values. I want to compute the similarity between column $x_3$ and columns $x_2$ and $x_1$. The similarity is computed by rows as ...
1
vote
1answer
19 views

Binomial model of true/false test taker

I have a very large number of true/false questions. I want to take a sample of these questions and use them to test a subject. I would like to infer the proportion of questions out of the larger set ...
1
vote
0answers
12 views

Is the Durbin-Watson test appropriate for count data

In determining if there is any serial correlation in a time series of count data, is the Durbin-Watson statistic or similar approaches appropriate? I ask this question because the dwtest implemented ...
0
votes
2answers
20 views

Significant difference and correlations

Something just came across my mind... Is it true that when there's no significant difference between groups then there will be correlations between groups? Can anyone clarify this?
0
votes
0answers
9 views

Regression from variable-length input vectors

I have a dataset that consists of variable-length categorical input vectors from which we would like to estimate the value of a numerical output variable. Is it possible to apply regression in this ...
0
votes
1answer
47 views

Difference between prediction in R and SQL

I'm working on a prediction model for a continuous variable (amount of medicine injected) .I use R for modeling.My project flow is to multiply the prediction of a glm (logistic regression) model that ...
1
vote
0answers
12 views

How to create a nearly orthogonal experimental design in R?

Does anyone know an R package for nearly orthogonal designs? I would like to create an experimental design, using 12 runs, up to 10 factors, and with mixed levels (e.g. a combination of 2 and 3 level ...
1
vote
1answer
15 views

divergence between nls (simple power equation) on non-transformed data and lm on log transformed data in R

I'm testing different ways to fit a simple power model to a dataset of 5 points. I don't get same results if I use nls on non-transformed data or lm on log10 transformed data in R whereas Excel ...
0
votes
0answers
6 views

R multinomial logistic regression interpretation

I have run a multinomial logistic regression test for the interaction between species of deer, days a camera trap was in the field and type of reaction. The model ...
0
votes
0answers
23 views

nMDS in vegan for soil data

I am working with abiotic soil data such as bulk density, moisture levels and soil chemistry as response data (some quantitative some as percentages) and a mix of abiotic and biotic data as ...
1
vote
0answers
4 views

How can I partition a distribution into two sub-populations with fixed bias? (simulation)

I am trying to simulate a selection model for a variable $Y$ dependent on covariate vector $X$, so that two groups/sub-sets $S=(0,1)$ of observations on $Y$ are created, which have a fixed difference ...
0
votes
0answers
9 views

Complete interpretation of Cox regression output in R

I need help with complete interpretation of this output(below). Can someone explain all (almost all) estimators in this output: what they mean and what is the substantive interpretation. In ...
3
votes
1answer
130 views

Making sense of scatter plots

I had a recent question which I probably should re-formulate to a more general one. I came across this: Using scatter plots to understand multiple values of Y for a given X and thought the accepted ...
2
votes
0answers
15 views

Plotting means in R [migrated]

I want to fit my vectors x ,y to some kind of curve, but they're both about 10k long with x-values very closely packed, so a scatter plot just ends up as a huge mess. What I'd like to do is to plot ...
0
votes
0answers
6 views

How to implement optimal scaling of categorical variables for fuzzy clustering?

I am referring this paper "Fuzzy e-Means Clustering of Mixed Databases Including Numerical and Nominal Variables" from IEEE for implementation and learning. Kindly correct my understanding so far: ...
0
votes
0answers
10 views

Probability of Multiple Observations of Multiple Objects

pr = physical RFID readers that are deployed on the production line in the factory. p(pr) = probability of the physical RFID reader. o = product part moving on the production line in the factory. O = ...
3
votes
3answers
970 views

Why is p for 8 times heads out of 21 flips not 8/21?

Flipping a fair coin 21 times. The probability of getting 8 heads in any order is $$p = \frac{21!}{8!(21-8)!}0.5^8(1-0.5)^{21-8} = 0.097$$ I get that the Binomial formula takes into account the ...
0
votes
0answers
8 views

Multiple regression with many zero values in DV, skewed data

I am not an expert, but I am trying to run a fixed effect multiple regression model in STATA. My data is panel data and has around 12000 observations, 348 districts over 36 months. My dependent ...
0
votes
0answers
10 views

What is the best ensemble sampler for highly correlated parameter space?

I have a likelihood that I want to estimate the free parameters for it and I am using MCMC to estimate the parameters. Two of the free parameters are positions and I defined uniform priors and one has ...
0
votes
0answers
25 views

Arima function doesn't consider seasonal components

Currently trying to fit several models to some data sets in order to find an accurate enough one, I ran into some difficulties with the Arima function of the ...
1
vote
1answer
16 views

Out-of-sample vs. test set

Someone asked me if I did out-of-time testing (which I assume is just out-of-sample testing but with a timeline element). But if I have a test set, is that not essentially the same as out-of-sample ...
0
votes
0answers
4 views

Explicit optimization of RIDGE penalization parameter

I work with a very simple setup: I have two possibly very correlated features $x_{1,2}$, with normaliazation such as $\text{var}(x_{1,2}) = 1$, $Ey = Ex_{1,2} = 0$ (for the empirical distribution). I ...
0
votes
0answers
7 views

How predictor importance in a cluster analysis (in SPSS) affected by dichotomy and multicollinearity?

I want to use a cluster analysis (CA) in SPSS to define different profiles in my dataset. I am using different continuous variables for this, including several neuropsychiatric measures. I am new in ...
0
votes
0answers
12 views

GLM with categorical predictor on R

I need to do a model with a generalized linear model. my data are thoses : habitat : O or 1, group : 1 or 0 , mortality : yes or no, and the numbers of individuals for each case. (habitat, group and ...
0
votes
0answers
3 views

Several categories using k-nearest neighbour

Is it possible to have a training data set for the k nearest neighbour with several categories likes 700 and about 10 attributes?
0
votes
0answers
13 views

I find very different results using a k-means or two-step clustering method. How is this?

I want to use a cluster analysis (CA) in SPSS to define different profiles in my dataset. I am using different continuous variables for this, including several neuropsychiatric measures. I am new in ...

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