# poisson.anova: Analysis of variance with a count variable In Rfast: A Collection of Efficient and Extremely Fast R Functions

## Description

Analysis of variance with a count variable.

## Usage

 ```1 2 3``` ```poisson.anova(y, ina, logged = FALSE) geom.anova(y, ina, type = 1, logged = FALSE) quasipoisson.anova(y, ina, logged = FALSE) ```

## Arguments

 `y` A numerical vector with discrete valued data, i.e. counts. `ina` A numerical vector with discrete numbers starting from 1, i.e. 1, 2, 3, 4,... or a factor variable. This is suppose to be a categorical predictor. If you supply a continuous valued vector the function will obviously provide wrong results. `type` This argument is for the geometric distribution. Type 1 refers to the case where the minimum is zero and type 2 for the case of the minimum being 1. `logged` Should the p-values be returned (FALSE) or their logarithm (TRUE)?

## Details

This is the analysis of variance with Poisson or geometric distributed data. What we do is a log-likelihood ratio test. However, this is exactly the same as Poisson regression with a single predictor variable who happens to be categorical. Needless to say that this is faster function than the glm command in R. For the same purpose with a Bernoulli variable use `g2Test`. The quasinpoisson.anova is when in the glm function you specify family = quasipoisson. This is suitable for the case of over or under-dispersed data.

## Value

A vector with two values, the difference in the deviances (or the scale difference in the case of quasi poisson) and the relevant p-value. The quasipoisson.anova also returns the estimate of the φ parameter.

## Author(s)

Michail Tsagris

``` logistic.cat1, g2Test, poisson.anovas, anova, poisson_only, poisson.mle ```

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```y <- rpois(300, 10) ina <- rbinom(300, 3, 0.5) + 1 a1 <- poisson.anova(y, ina) a2 <- glm(y ~ ina, poisson) ## Not run: res<-anova(a2, test = "Chisq") ## End(Not run) y <- rgeom(300, 0.7) res<-geom.anova(y, ina) ```

### Example output

```Loading required package: Rcpp