R Under development (unstable) (2025-05-29 r88251 ucrt) -- "Unsuffered Consequences"
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> library('mfx')
Loading required package: sandwich
Loading required package: lmtest
Loading required package: zoo

Attaching package: 'zoo'

The following objects are masked from 'package:base':

    as.Date, as.Date.numeric

Loading required package: MASS
Loading required package: betareg
> 
> ### Name: poissonmfx
> ### Title: Marginal effects for a Poisson regression.
> ### Aliases: poissonmfx print.poissonmfx
> 
> ### ** Examples
> 
> # simulate some data
> set.seed(12345)
> n = 1000
> x = rnorm(n)
> y = rnegbin(n, mu = exp(1 + 0.5 * x), theta = 0.5)
> 
> data = data.frame(y,x)
> 
> poissonmfx(formula=y~x,data=data)
Call:
poissonmfx(formula = y ~ x, data = data)

Marginal Effects:
     dF/dx Std. Err.      z     P>|z|    
x 1.460085  0.042913 34.025 < 2.2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
> 
> proc.time()
   user  system elapsed 
   0.60    0.07    0.62