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Questions tagged [poisson]

The Poisson distribution is a statistical discrete distribution for describing events occurring at random intervals. It is defined on the non-negative integers that has the property in which the mean is equal to the variance.

The Poisson probability distribution is used to model the probability of a number of events occurring during a specified time interval.

The Poisson distribution is characterized by an expected arrival rate, usually designated by the Greek lower-case letter lambda.

A discrete random variable X has a Poisson distribution indexed by a parameter λ if it has probability mass function as following:

enter image description here

Useful links:

Wikipedia entry for the Poisson distribution.

How do I generate discrete random events with a Poisson distribution?

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Poisson Regression Model Issue

I am trying to predict the count for a particular data set over varying time periods. Hence, I'm using an offset to account for these different time periods. However, while trying to fit the model I get this error: LinAlgError: Singular matrix I…
Niranjan
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Adding poisson noise to an image with specific mean.

How do I add Poisson noise with a specific mean of Poisson distribution in Matlab? The code below gives me a completely white image. img = im2double(phantom(512)); figure; imshow(img) mean = 1e9; R = poissrnd(mean, [512, 512]); J = img + R; figure;…
ddxxdds
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Fitting a lognormal or poisson distribution

I have a vector of 1096 numbers, the daily average concentration of NOx measured in 3 years in a measurement station. You can observe the type of distribution in the image: I used these commands to do the…
Silvia
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R fitting quasipoisson glm with joint modeling of dispersion

I'd like to fit a quasipoisson model with joint modeling of dispertion parameter. I have 3 quelitatives covariates, so the parameters to estimate are indexed on i,j,k. The model is : I want to differentiate the $\phi$ on the covariates, and…
lrnv
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Deviation of random effect stuck at 0 for underdispserd poisson data

I recently found a rather unexpected behavior of glmer for underdispersed data: the number of eggs laid in 4 nestboxes placed in 53 forest plots. The standard deviation estimates get stuck at 0 even if there are quite some between-group variation…
Lionel
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Lightgbm with Tweedie

I'm trying to run lightgbm with a Tweedie distribution. I believe this code should be sufficient to see the…
Simon Todd
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R: How to split a bimodal distribution in two, and calculate probabilities of samples being in either

I have a bimodal distribution consisting of two poisson distributions as graphed below. I would like to divide the bimodal distribution into two poisson distributions, such that I for each sample have the probability of it being in either of the…
Esben Eickhardt
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Incorrect results with Poisson regression using bambi?

I am giving bambi (version 0.1.0) a try for a simple Poisson regression model. However the results differ when compared to straight pymc3 or statsmodels implementations, and I cannot seem to figure out how to interpret the coefficients that bambi…
user3083667
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Python .append seems to run forever and the 'uniform' value seems not too random (making Poisson sphere distribution in Python)

I am now trying to calculate the poisson sphere distribution(a 3D version of the poisson disk) using python and then plug in the result to POV-RAY so that I can generate some random distributed packing rocks. I am following these two…
Ari
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Constructing a predictive model for unbalanced panel data with positive discrete dependent variable in R

I am trying to construct a predictive model for a dataset with a dependent variable (Y) which consists of non-negative integer values with a maximum of 100. Below is a histogram plot of Y which shows its very much skewed to the right. Furthermore, I…
Michael
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MLE bootstrap on poisson distribution

I have the following Poisson distribution: Data 3 5 3 1 2 1 2 1 0 2 4 3 1 4 1 2 2 0 4 2 2 4 0 2 1 0 5 2 0 1 2 1 3 0 2 1 1 2 2 0 3 2 1 1 2 2 5 0 4 3 1 2 3 0 0 0 2 1 2 2 3 2 4 4 2 1 4 3 2 0 3 1 2 1 3 2 6 0 3 5 1 3 0 1 2 0 1 0 0 1 1 0 3 1 2 3 3 3 2…
Jamie Leigh
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Obtaining correct confidence intervals for Poisson rate ratio test

In R I am having a problem obtaining exact confidence intervals for the rate ratio as calculated by the poisson.test function. This function uses the method in binom.test to calculate the confidence limits between two rates e.g. poisson.test(x =…
Svencken
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Enumerate all possible combined probabilities of a series of Bernoulli trials with different probabilities

Suppose I have a series of n probabilities for success of independent Bernoulli trials, p1 to pn such that p1 != p2 != ... != pn. Give each trial a unique name. p <- c(0.5, 0.12, 0.7, 0.8, .02) a <- c("A","B","C","D","E") I know from…
paqmo
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Why is the likelihood/AIC of my poisson regression infinite?

I am trying to evaluate themodel fit of several regressions in R, and I have run into a problem I have had multiple times now: the log-likelihood of my Poisson regression is infinite. I'm using a non-integer dependent variable (Note: I know what I'm…
nickbloom
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Using CARET together with GAM ("gamSpline" method) in R Poisson Regression

I am trying to use caret package to tune 'df' parameter of a gam model for my cohort analysis. With the following data: cohort = 1:60 age = 1:26 grid = data.frame(expand.grid(age = age, cohort = cohort)) size = data.frame(cohort = cohort, N =…
Nick Mars
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