Hello! I have gotten a bit farther working on my shiny R code. I am trying to make a game for students to practice estimating the standard deviation of a set of data using a histogram and a chosen sample size. I am having trouble making it a scored game where the student must submit their guess, followed by feedback and a change in their score.

```
library(shiny)
# Define UI for application that draws a histogram
ui <- fluidPage(
# Application title
titlePanel("Standard Deviation Estimation Practice"),
# Sidebar with a slider input for sample size
sidebarLayout(
sidebarPanel(
sliderInput("samplesize", h3("Enter a positive whole number as a sample size"), min = 10, max = 500, value = 250),
actionButton(
inputId = "submit_hist",
label = "Press for new Histogram"),
numericInput("guess", "What is your estimation of the standard deviation of the data in the histogram?", ""),
actionButton(
inputId = "submit_guess",
label = "Press to Submit Guess"),
tags$style("body{background-color: white; color: black}")
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("distPlot"),
textOutput("result")
)
),
sidebarLayout(
sidebarPanel("Made for Introductory Statistics for Biology", width = 3),
mainPanel("score"),
))
# Define server logic required to make a histogram
server <- function(input, output){
x_val <- eventReactive(input$submit_hist, {
seed1 <- sample.int(1000000, 1)
set.seed(seed1)
sd1 <- sample.int(25, 1)
mean1 <- sample((-300):400, 1)
rnorm(n = req(input$samplesize), mean = mean1, sd = sd1)
})
y_val <- eventReactive(input$submit_hist, {
sd(req(x_val()))}
)
output$distPlot <- renderPlot({
# draw the histogram with the specified sample size
hist(req(x_val()),
main = "Histogram",
xlab = "Sample Values",
ylab = "Frequency Count",
col = "darkgray",
border = "white"
)
})
output$result <-
eventReactive(input$submit_guess, {
q <- input$guess
# print(y_val())
ifelse(q() >= (y_val() - 1.0), ifelse(q() <= (y_val() + 1.0),
"That is a correct estimation! Good job! Enter a new sample size.",
"That estimate is too big. Try again!"),
"That estimate is too small. Try again!")
})
output$score <- {counter <- reactiveValues(countervalue = 0)
observeEvent({(q() >= (y_val() - 1.0)) & (q() <= (y_val() + 1.0))}, {
counter$countervalue = counter$countervalue + 1})
observeEvent({(q() <= (y_val() - 1.0)) | (q() >= (y_val() + 1.0))}, {
counter$countervalue = counter$countervalue + 0})
output$score <- renderText({paste("Your Score is ", counter$countervalue)})
}
}
# Run the application
shinyApp(ui = ui, server = server)
```

below is the code for a simpler version of the app that worked before (thanks for the help, Nir)

```
library(shiny)
# Define UI for application that draws a histogram
ui <- fluidPage(
# Application title
titlePanel("Standard Deviation Estimation Practice"),
# Sidebar with a slider input for sample size
sidebarLayout(
sidebarPanel(
sliderInput("samplesize", h3("Enter a positive whole number as a sample size"), min = 10, max = 500, value = 250),
actionButton(
inputId = "submit_hist",
label = "Press for new Histogram"),
numericInput("guess", "What is your estimation of the standard deviation of the data in the histogram?", ""),
tags$style("body{background-color: white; color: black}")
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("distPlot"),
textOutput("result")
)
),
sidebarPanel("Made for Introductory Statistics for Biology", width = 3)
)
# Define server logic required to make a histogram
server <- function(input, output){
x_val <- eventReactive(input$submit_hist, {
seed1 <- sample.int(1000000, 1)
set.seed(seed1)
sd1 <- sample.int(25, 1)
mean1 <- sample((-300):400, 1)
rnorm(n = req(input$samplesize), mean = mean1, sd = sd1)
})
y_val <- reactive({
sd(req(x_val()))
})
output$distPlot <- renderPlot({
# draw the histogram with the specified sample size
hist(req(x_val()),
main = "Histogram",
xlab = "Sample Values",
ylab = "Frequency Count",
col = "darkgray",
border = "white"
)
})
output$result <- renderText({
q <- req(input$guess)
if (!isTruthy(q)) {
return(NULL)
}
# print(y_val())
ifelse(q >= (y_val() - 1.0), ifelse(q <= (y_val() + 1.0),
"That is a correct estimation! Good job! Enter a new sample size.",
"That estimate is too big. Try again!"),
"That estimate is too small. Try again!")
})
}
# Run the application
shinyApp(ui = ui, server = server)
```

Now it aborts the program when running all together. Thank you for your help.