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Parameter Tuning for auto-regressive Neural networks (NNETAR)

I am analyzing time series data on electricity prices using a variety of methods (ARIMAX, TBATS, STLM) including the auto-regressive feed-forward neural network NNETAR, which is implemented in the ...
0
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0answers
87 views

How to find parameter $k$ from a negative binomial distribution in R?

I want to find the value of parameter $k$ from my data set. The data set is composed of several populations. Should I calculate the parameter $k$ for each subpopulation, or for the population at large?...
0
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0answers
38 views

How to test for differences between model parameter estimates for different datasets?

Description of analysis I am considering grain yield response to available nitrogen with a linear-plateau piecewise regression model for two different field studies, denoted by the variable ...
1
vote
1answer
83 views

How to identify a Bayesian SEM parameter in R package blavaan

I have fit a Bayesian SEM using the R package blavaan. ...
-1
votes
1answer
39 views

use data of table in R [closed]

I have a table of data that I have already imported in R as variable Dataset and I want to apply the function fitdistr() to my ...
1
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0answers
73 views

Basics of Akaike's Information Criterion in GIS/Hydrology

I have been asked to use the AIC to assess the relative fitness of various terrain wetness index (TWI) methods for predicting soil moisture in a specific study site. The TWI is calculated from a ...
3
votes
1answer
588 views

Fitting t-distribution to data and deriving moments

I'm fitting the t-distribution to financial data and I know of two methods to do this using R: (A) fitdistr(mydata, "t") Output: ...
0
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1answer
304 views

SVM gamma parameter influence : 2moons data set

I'm working on the two-moons data set, in which we can achieve a perfect discrimination, the classes are separable. I'm using the RBF kernel, and as a consequence, i have to tune the gamma parameter. ...
1
vote
0answers
154 views

Data simulations for SVM : study of parameters

I'm studying SVM for classification. The first step of my work consists in making a data simulation in order to study the influence of the cost parameter C, the choice of the kernel, for examples. Do ...
2
votes
1answer
970 views

Holt-Winters parameters in R

I'm trying to replicate some values from a holt winters calculation made in excel by someone else. I have the time series time_x, and I'm using the forecast package. The problem is when I run the ...
0
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0answers
122 views

What do the parameters A, B, and C do in an equation of the form $Y = A + Be^{CX}$? [duplicate]

I have read this article and those linked to it, but I am still having difficulties fitting a function of this form to data I have using the nls function in R. Invariably, I fail to get convergence ...
1
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1answer
100 views

Tune parameters from a specific equation in R

This is the first time I am truing to tune model parameters in R. I have a fairly complicated equation with multiple parameters: ...
5
votes
2answers
4k views

How to interpret slope parameter estimates for linear models in R?

I wish to analyse a simple lab experiment. I have 8 fish. Four are fed on diet A, and four on diet B. I measure their Nitrogen (N) over 5 time periods (so 5 repeated measures per fish). I wish to know ...
1
vote
1answer
159 views

Beta binomial mean different from actual mean

I have data that I am fitting a beta binomial distribution to. The VGAM package for R is being used to do this. However, the the mean of the fitting beta binomial distribution is vastly different from ...
0
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0answers
85 views

forcing certain parameters to be skipped during optim in R

I have a code which tests each possible order of ARIMA and selects the best model by choosing the one with the absolute minimum sum of lags from the PACF graph. The code then proceeds to add weight to ...
2
votes
1answer
2k views

Likelihood ratio test for comparing two exponential distributions

I am trying to use a likelihood ratio test to compare the parameters of two exponential distributions. by this thread Likelihood Ratio for two-sample Exponential distribution I found that I can use ...
4
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2answers
2k views

Confusing Holt-Winters parameters

I have got a model for forecasting using holt-winters. However the parameters confuse me... The parameters show that there is no trend or seasonality even though there is definite trend and ...
3
votes
1answer
619 views

Smoothing parameter for spline curve with duplicate points

I have body mass and age data for a population of individuals. I want to fit a cubic smoothing spline curve to the data. I'm using smooth.spline in R, which warns against using cross-validation to ...
4
votes
1answer
1k views

What is the parameterization of exponential distribution for survival in Stata?

I'm new to data analysis so this is kind of a simple question. I would like to understand why I cannot reproduce a survival curve generated by a fitted exponential model from Stata. I use the ...
7
votes
2answers
7k views

How to use the SD of a normal sampling distribution to specify the gamma prior for the corresponding precision?

The gamma distribution is a commonly used prior distribution for the precision ($1/sd^2$) of a normal distribution in Bayesian hierarchical modeling. I want to use an informed prior for the variance ...
0
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1answer
724 views

Compound Poisson, preliminary work in R

I need help with following programming code: Beforehand: I tried to estimate Poisson-parameters, but M.L.E. and M.C. do not give satisfactory results regarding actual to expected, from actuarial ...
12
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2answers
3k views

Random Forest: what if I know a variable is important

My understanding is the the random forest picks randomly mtry variables to build each decision tree. So if mtry=ncol/3 then each variables will be used on average in 1/3 of the trees. And 2/3 of the ...
31
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1answer
6k views

For which distributions are the parameterizations in BUGS and R different?

I have found some distributions for which BUGS and R have different parameterizations: Normal, log-Normal, and Weibull. For each of these, I gather that the second parameter used by R needs to be ...