 # Error with wp.poisson function for Power Analysis

I am trying to do a power analysis to determine the sample size for Poisson glm regression that I plan to do once I have my experiment data.
The only function that I have been able to find to calculate sample size for Poisson is wp.poisson() in the WebPower package. However, when I run the function (below) I get the resulting error:

``````wp.poisson(n = NULL,
exp0 = 5.0345,
exp1 = 1.5862,
alpha = 0.05,
power = 0.8,
alternative = "two.sided",
family = "Poisson",
parameter = 1)

``````

Error in uniroot(function(n) eval(p.body) - power, c(2 + 1e-10, 1e+07)) : f.lower = f(lower) is NA

``````Can someone help me figure this out?
Alternatively, does anyone know how else to do power analysis to determine sample size for a Poisson regression?

Thank you.``````
``````library(WebPower)
library(purrr)
library(plotly)

params <- expand.grid(exp0_v = seq.default(from=0,to=2,by=.2),
exp1_v = seq.default(from=0,to=2,by=.2))

params\$n_result <- map2_dbl(.x=params\$exp0_v,
.y=params\$exp1_v,
.f=~tryCatch(wp.poisson(n = NULL,
exp0 = .x,
exp1 = .y,
alpha = 0.05,
power = 0.8,
alternative = "two.sided",
family = "Poisson",
parameter = 1)\$n
, error = function(e) NA)

)
plot_ly(data=params,
x=~exp0_v,
y=~exp1_v,
z=~n_result,
type="scatter3d", mode="markers", color=~n_result,
text=~paste0("exp0 : " ,exp0_v, "\n",
"exp1 : " ,exp1_v, "\n",
"n_result : " ,n_result, "\n"),
hoverinfo="text")
``````

with the other params you set, values above 1 for exp1 will give NA values due to infinities in the calculations

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Thank you for sharing!