Hi!

I'm new to programming shiny apps. I did work with R a bit before for clinical research.

Can anyone please help me with getting this code running? I'm trying to build a simple sample size calculator for the comparison of 2 independent proportions, using a function from the pwr package.

The function is `pwr.2p.test(h = , n = NULL, sig.level = , power = , alternative = ("two.sided","greater", "less"))`

with `h <- ES.h(p1, p2)`

calculating Cohen's effect size (`2*asin(sqrt(p1))-2*asin(sqrt(p2))`

)

n is the number of patients required per group - this is what I'm after.

I would like the user to be able to adjust the other variables in a reactive way (see my input code).

This is what I've come up with:

```
install.packages(c("pwr", "powerSurvEpi"))
library(pwr)
library(shiny)
ui <- fluidPage(
titlePanel("Sample Size Calculator - Proportions"),
sidebarLayout(
sidebarPanel(
radioButtons(inputId="power", "Power level:", c("0.80", "0.90"), selected = "0.80"),
radioButtons(inputId="significance", "Significance level/Alpha:", c("0.01", "0.05", "0.10"), selected = "0.05"),
radioButtons(inputId="type", "Two or one-sided test:", c("two.sided", "greater", "less"), selected = "two.sided"),
numericInput(inputId="p1", "Proportion group 1", value=0.00, min=0, max = 1, step=0.10),
numericInput(inputId="p2", "Proportion group 2", value=0.00, min=0, max = 1, step=0.10),
br(),
br(),
actionButton("button", "Calculate sample size")
),
mainPanel(
tags$h4("Your required sample size per group:"),
verbatimTextOutput(outputId="samplesize")
)
))
server <- funtion(input, output) {
eventReactive(input$button,{
h <- ES.h(input$p1, input$p2)
result <- pwr.2p.test(h=as.numeric(h), n=NULL, sig.level=as.numeric(input$significance), power=as.numeric(input$power), alternative=input$type)
})
output$samplesize <- renderPrint({result[2]})
}
shinyApp(ui = ui, server = server)
```

I did try to get it working in many different ways, but I get some error messages in the console:

- Error: unexpected '{' in "server <- funtion(input, output) {"
- Error in output$samplesize <- renderText({ : object 'output' not found

And I simply do not get the app to show the calculated n in the output frame.

Anyone? A million thanks in advance!