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Getting distances from points to their principal curve projections in R princurve? [closed]

I have been using the R package, princurve, to calculate principal curves. Now I want to obtain the squared distances from the points I used to fit the principal curve to their projections in the ...
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How can I estimate the variance of the error terms in a conditional/multinomial logit model?

Conditional/multinomial logit models(CML) can be esimated by the Maximum Likelihood Estimation(MLE). The likelihood would consists of choice probabilities: \begin{equation} P_{ij}=\frac{e^{V_{ij}}}...
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Shrinkage / L1 regularization as a loss term versus a constraint (post-process step) with momentum optimizers

I have a complex model with very non-linear operations (divisions, exponentials, matrix inversions, square roots, Cholesky decompositions, etc...) for which I want to optimize the parameters. However, ...
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1 answer
31 views

Problem formulating a hypothesis test for the mean

Suppose that I would like to support the following hypothesis: h = The average weight of people in New York is 70kg. If I take h to be the null hypothesis then I can only reject it (I assume that ...
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Should I join train and validation sets for final NN model training? If yes, when to stop training the final model?

Normally we divide our dataset into 3 sets: train set, validation set, test set. We use train set to find optimal parameters (weights and biases of NN) and validation set to find optimal NN ...
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How to run a multilevel regression model with crossed random effects: items and participants?

I am trying to run a multilevel regression for my study: I have two random effects; participants (97) and items (which are the 20 words used in the study) Each participant had to spell the same words. ...
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1 vote
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is nrmse scale-dependent?

Im trying to evaluate my regression models using a normalised version of the RMSE, nrmse = rmse(y, y_pred)/rmse(y, y_mean) where y_mean is the array of the same len as y filled with the mean value of ...
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How do you get this bifurcation diagram of this 2D discrete time model?

I want to replicate the results of "Chaos in Duopoly Pricing" by T. Puu, which can be found here: https://www.sciencedirect.com/science/article/pii/096007799190045B#section-cited-by. The ...
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1 vote
0 answers
26 views

Mean-level forecast from rugarch does not match manual calculation

I am looking into the rugarch package and am trying to understand how the one-step-ahead forecast is calculated. Specifically, I am fitting an AR(2)-GARCH(1,1) ...
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33 views

Estimating Top n Prices points on a given day for a particular product which would maximize revenue

Problem Statement :- On any given date of the year, get top n prices which would maximize the revenue for that day for a particular platform. Dataset :- Date Price ($p_{i}$) Platform $X_{1,i}$, $X_{...
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LinearRegression in Pytorch and sklearn, what is the differnece?

I am currently implementing Linear Regression in Pytorch and sklearn and I get two different Mean squared error (MSE) values for both. MSE is lower for Pytorch Linear Regression. Wanted to ask what ...
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Interpret output for the standardised difference in stata [closed]

I have an output for the standardised difference using the stddiff command in Stata. How do I interpret it?
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1 vote
0 answers
16 views

What is a differentiable approximation to the indicator function a != b [closed]

I am dealing with an optimization problem where I'd like to regularize two parameters $a$ and $b$. The penalty should be $1$ if the parameters differ and $0$ if they are the same. The motivation is ...
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Why the author is quite loose when controlling in control variables for exchange rate regression? [closed]

I read a paper from (Han 2020) and from his equation (4) Δ s ...
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27 views

Power / sample size estimation for chi-square test with continuity correction in R

1._Some authors mention that they estimate sample size for chi-square test with continuity correction. For instance: Sample-size calculation is based on Pearson's Chi-square test with a two-sided ...
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1 vote
2 answers
63 views

Is it normal for simple logistic regression to significantly outperform any other statistical ML algorithm?

I'm working on a simple classification project with an imbalanced (minority-to-majority-ratio ~ 0.2) dataset that has ~4000 rows and ~200 features. I noticed that, for my dataset, a simple logistic ...
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1 vote
0 answers
8 views

Encoding Geolocation data

I am working on routing bus from one stop to another, for which Geolocation data inform of latitude and longitude is required. In addition to xy coordinates, distance matrix of locations is also ...
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5 votes
2 answers
388 views

Is "Uncensored Data" necessarily more "Informative" when compared to "Censored Data"?

I am told that one of the main benefits of Survival Analysis models are their ability to handle Censored Data. This is in contrast to standard regression models that are unable to do so. For example, ...
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1 answer
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Formal definition of "sampling intensity" in terms of probability theory

This wiki on forest inventory and remote sensing has various pages related to sampling concepts and methods. They define sampling intensity as follows: Sampling intensity refers to the proportion of ...
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1 answer
26 views

How to select a time series model based on this ACF?

I think that I am missing some concepts because I am not able to model adequately this series. It is a times series over 12 years. I tried with multiple AR and MA models, nevertheless, I can't model ...
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28 views

Using machine learning model trained on standardized data for real world low volume data

I have developed a machine learning model which has been trained on a preprocessed data by scaling and centering using h2o package of R. I am able to use this model ...
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  • 197
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0 answers
10 views

Multivariate analysis of sample mean and sample variance

$\{X_n\}$ Let be a sequence of iid probability vectors with mean vector$ \mu$ and variance-covariance matrix$ Σ$. In this case, sample variance and sample covariance are defined as follows $S_{n,j}^2=\...
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2 votes
0 answers
17 views

is ok to use the same variable in two hierarchies?

I have a dataset with two levels: the city level and person level, at the city level i have the categorical variable "poverty level", in my research estimating the effect of the "...
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1 vote
0 answers
8 views

Scientific reporting of time-varying covariates at different time frequencies

Say I have the following model: $$y_{it} = \gamma_i + \delta {T}_{it} + \zeta Z_{i(k)} + \epsilon_{it}$$ where $y$ is some outcome for household $i$ in month $t$. $\gamma_i$ denotes household fixed ...
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1 vote
0 answers
17 views

Balancing Multiple Evaluation Metrics for a Model

When evaluating a machine learning (or other statistical model) against multiple evaluation metrics, is there a standardized way to choose the "best" model? As a concrete example, for a two ...
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0 answers
32 views

How to generate a latin square for a user study?

I have to do a user study for a paper to see how using or not using tool X affects the quality of something (defined in my study). The study goes like this: participant 1 uses tool X to do task A and ...
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4 votes
1 answer
128 views

Simulating a joint distribution with the inverse method

I have the following joint distribution: $$f(x, y) = 3x^2y^xe^{-x^3}(1 + x),\quad x \gt 0,\ y \in (0,1).$$ I want to simulate a sample of this distribution through the inverse method but I don't know ...
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1 answer
25 views

Chi square for three categorical variables

Can I use chi square test with three variables ? The variables are organizational climate (11 dimensions), job satisfaction (7 dimensions) and customer satisfaction (5 dimensions). Likert scale. any ...
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0 answers
15 views

Best way to approximate head point having only face keypoints

I'm using the BlazeFace model from TensorFlow which only has this few keypoints: I need those keypoints plus a head keypoint, like this one: My question is, which would be the best way to ...
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0 votes
1 answer
20 views

Conflicting ACF/PACF after first-difference

I have yearly data. When I do a Dickey-Fuller test it gives me insignificant results, indicating that the series are non-stationary. After differencing them the DFT tells me they are now significant ...
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12 views

How to avoid having very different examples inside a cluster with Kmeans?

Let's say I've created some clusters with Kmeans using 5 features, the Silhouette Score for these cluster are very high, higher than 0.8, and The within-cluster sum of squares is around 130 in this ...
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17 views

Can we train normalizing flows with Wasserstein distance?

To train flow based models, you usually either use forward or reverse kl as your loss function. My question is, can you use wasserstein distance directly as your loss function to replace kl? I have ...
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1 answer
8 views

I think coxph post estimation with big data - confused about the results

I am having trouble understanding if my data is cooked, and how bad, based on post-estimations for coxph. The regression and the cox.zph test is below. Based on the post-estimation, this looks bad ...
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  • 155
0 votes
1 answer
37 views

Distribution of the Spearman rank correlation coefficient under the assumption of non-zero correlation

There are some papers and some R packages providing exact calculations for the CDF and the inverse-CDF of the (sample) Spearman rank correlation coefficient. My question is: How difficult would it be ...
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1 vote
1 answer
13 views

Comparing goodness of fit across parametric and semi-parametric survival models

I've been learning about time-to-event analysis and playing with open datasets + fitting various Cox and parametric models for practice. Other than by visually inspecting the estimated survival curves ...
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0 answers
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Which are well-known/popular feature selection methods? [duplicate]

I am trying to test the performance of first reducing the number of features before applying methods such as neural networks for prediction. Due to the fact that the number of observations is not ...
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0 answers
49 views

Generate given percentile (or data) from n, mean, median, standard deviation, p1, p25, p50, p75, p99?

I apologize if this should be asked elsewhere. I have the following information: Where N=1808 I am trying to calculate a given percentile (in this case p99.723), or ideally, if possible, generate ...
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0 votes
1 answer
27 views

Help with Excel's Regression Output

I'm a junior engineer at a small biotech company and have some (real) data from a fractional factorial DoE (3 factors, 2 levels, 4 test conditions with six replicates each). Currently, we use excel to ...
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0 answers
14 views

Combining data from multiple studies - best approach?

I'm looking at an old paper on the incidence of HPV infection by age cohorts. The authors present a plot of estimates from many different studies around Europe which looks like this - note the authors ...
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  • 197
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0 answers
19 views

Should you clean your data after or before selecting a sample?

Assuming a 500k dataset. For statistical modeling purposes (selecting up to 10% of 500k as a sample). Should I clean the 500k dataset first before selecting a sample or select the sample first and ...
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0 votes
1 answer
43 views

football probability

I have the following problem: Suppose that the probability of a football team (T) to win the match with 2-1 is p1 and, given that T scores a goal, the probability that the best player of the team ...
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0 votes
0 answers
8 views

Setting up a stacked dataframe for multilevel model analysis in R

I need to set up my data frame into a stacked or long form in order to do a random crossed effects multilevel analysis. My random factors are participants and items (words in the assessment) My fixed ...
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0 votes
0 answers
5 views

How to get the Operational items by finer frequency than annual [closed]

I am looking for the availability of some operation items of firms including (Total Assets Turnover- WC08401, Inventory Turnover -WC08136) with a frequency finer than annually from Datastream (...
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0 votes
0 answers
15 views

How to conduct t-test for comparing the accuracy of two binary classifiers? [closed]

I am using two binary classifiers that predict the accuracy of samples over a dataset. I need to check if the difference in the mean accuracy between the two models is statistically significant. ...
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0 answers
10 views

Metropolis and Barker Algorithms: Irreducibility

A question from Brémaud, Markov Chains Gibbs Fields, Monte Carlo Simulation and Queues. Exercise 11.5.2. Metropolis and Barker Algorithms: Irreducibility how do you show explicitly that $$p_{i,j}= \...
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  • 1
0 votes
1 answer
27 views

Distribution function of the linear combination of standardized student-t quantiles [duplicate]

Assume to observe 2 quantiles, x and y, associated with the z% probability. These quantiles are generated by 2 non-independent standardized student-t distributions X and Y. In case of linear ...
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0 answers
7 views

Validation Loss for my binary image classifier model is increasing. how to bring it down? [duplicate]

I am new to the domain of Deep learning and I have been trying to create a binary image classifier using a dataset which I created by myself. I am building the model from scratch. It is CNN model. ...
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  • 1
0 votes
0 answers
19 views

Balancing a dataset in object detection through data augmentation and then random oclusion of classes?

first of all some info about the model I'm using. I'm using YOLOR, which uses a YOLOV5 formatted dataset. I'm trying to detect components off of PCB's which are divided into some groups (visible on ...
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21 views
+50

Choosing response and predictors

Information on the Girth (), Height () and Volume () for 31 cherry trees yielded the following correlations : $r_{12}$ = 0.519, $r_{23}$= 0.598 and $r_{13}$= 0.967. If you were asked to setup a ...
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  • 83
1 vote
0 answers
10 views

How do I perform a train-validation split on data with class imbalance such that the class imbalance ratio is preserved?

My data has class imbalance-- that is, some classes have significantly fewer training samples than the others. I want to perform a train-validation split in such as way that the class ratios are ...
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