app.R

library(shiny)

ui <- fluidPage(

    titlePanel("How Many Reviewers?"),

    sidebarLayout(
        sidebarPanel(
            numericInput("n_papers", "Number of Anticipated Papers", 100),
            numericInput("n_reviews", "Number of Reviews Per Paper", 3),
            tags$hr(),
            numericInput("n_reviews_per_reviewer", "Number of Papers Per Reviewer", 10),
            numericInput("pct_accept", "Anticipated % of Invited Reviewers Who Accept", 80),
            tags$hr(),
            tags$p("Source: https://gist.github.com/jrosen48/cda351a1437d06cf74d77679afb4b6b0")
            
        ),

        mainPanel(
           textOutput("total_reviewers")
        )
    )
)

server <- function(input, output) {

    observeEvent(TRUE, {
    output$total_reviewers <- renderText({
        total_reviews <- input$n_papers * input$n_reviews
        expected_per_reviewer <- input$n_reviews_per_reviewer * (input$pct_accept/100)
        paste0("Invite ", ceiling(total_reviews / expected_per_reviewer), " reviewers")
    })
    })
}

shinyApp(ui = ui, server = server)