Questions tagged [gamlss]

Generalized additive models for location, scale and shape (GAMLSS).

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26 votes
3 answers

Regression modelling with unequal variance

I would like to fit a linear model (lm) where the residuals variance is clearly dependent on the explanatory variable. The way I know to do this is by using glm with the Gamma family to model the ...
Tal Galili's user avatar
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5 votes
1 answer

Are there better approaches than the weighted mean?

If I have a data set where the distribution from which the data are drawn changes, for example in the following plot, the data set is comprised of four normal distributions with the same mean ($\mu = ...
user27119's user avatar
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10 votes
2 answers

Simulate linear regression with heteroscedasticity

I am trying to simulate a dataset that matches empirical data that I have, but am unsure how to estimate the errors in the original data. The empirical data includes heteroscedasticity, but I am not ...
user44796's user avatar
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11 votes
1 answer

Zero inflated beta regression using gamlss for vegetation cover data

My goal is to analyse vegetation cover data. The way the data collection works is that you throw a quadrat (0.5m x 0.5m) in a sample plot and estimate the percent cover of the target species. Here is ...
Stefan's user avatar
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11 votes
3 answers

fit GLM for weibull family [closed]

I am trying to fit generalized linear model for weibull family, but when I try it in R, it gives an error. I know that weibull does not fit in exponential family, but I have read some research ...
NiroshaR's user avatar
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11 votes
1 answer

Convert SAS NLMIXED code for zero-inflated gamma regression to R

I'm trying to run a zero-inflated regression for a continuous response variable in R. I'm aware of a gamlss implementation, but I'd really like to try out this algorithm by Dale McLerran that is ...
a11msp's user avatar
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6 votes
2 answers

Modelling zero-inflated proportion data in R using GAMLSS

I am new to the gamlss package and would like to check that I am using the correct family for proportion data (tree species cover after treatment), which is bounded ...
Alex Picard's user avatar
1 vote
1 answer

How to find the appropriate model to apply (GAMLSS)/Approving statistical thinking

I need to compute percentile curves using the LMS method (from the GAMLSS package/models) with Age and Height as predictors. What is the best way to determine which equation (with which transformation ...
stats's user avatar
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28 votes
1 answer

What diagnostic plots exists for quantile regression?

Following on my question for OLS, I wonder: what diagnostic plots exists for quantile regression? (and are there R implementation of them?) A quick google search already came up with the worm plot (...
Tal Galili's user avatar
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8 votes
3 answers

How to model zero inflated, over dispersed poisson time series?

I am trying to model weekly disease counts in 25 different regions within 1 country over a ten year period as influenced by temperature. The data is zero inflated and over dispersed. I am most ...
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4 votes
3 answers

Is it possible to calculate variable confidence intervals, conditional on $\hat{Y}$ to address heteroscedasticity?

Estimating confidence intervals for non-normally distributed residuals can be accomplished using bootstrapping procedures, sandwich estimators or quantile regression. But is there a way to calculate $...
Robert Kubrick's user avatar
3 votes
1 answer

What distribution has exactly three parameters for mean, variance, and skewness?

Common distributions usually fix their skewness. Beta distribution has two parameters to determine all of the mean, variance, and skewness. Student-T's skewness can change by some definitions but it ...
High GPA's user avatar
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3 votes
0 answers

What is Mu in zero/one beta inflated models? (gamlss (BEINF))

I am estimating a zero/one inflated beta regression model with gamlss (family BEINF). My dependent variable is [0,1] with a lot of 0s, quite some 1s, and some values in between. This means I assume ...
user33125's user avatar
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2 votes
0 answers

How to correctly specify and diagnose one-inflated beta regression mixed-models (using GAMLSS)

I would like to find out what variables influence/explain an efficiency score for an invasive species control method. As the score is defined on (0,1] and as some observations were not independent, I ...
Fanfoué's user avatar
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2 votes
1 answer

Mann Whitney test, unequal sample sizes, different=shaped continuous proportions plus many zeros

I was hoping someone could help, I am comparing proportional data in to two different groups. One group has a sample size of 22 and the other 530. The data are not normally distributed and have ...
user3237130's user avatar
1 vote
0 answers

Why do different negative binomial regression functions produce different coefficients, p-values

I have a dataset consisting of number of mutations per person. Covariates I think may be related are age and source of the DNA sample. I want to determine whether the disease the person has ...
Jessica's user avatar
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0 votes
1 answer

Articles that work with covariates for mean, variance, and correlation simultaneously

Does anyone know of articles in which, in addition to modeling the mean parameter, are also modeled the variance and correlation parameters? I know the double generalized linear model, but they only ...
fsbmat's user avatar
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