Warning: Error in as.character: cannot coerce type 'closure' to vector of type 'character'

Doing a small project for homework. We had to copy beginner project code from a book and then edit the slider into the sidebar. I copied the work in the book but get an error every time I try to run the app.

>Warning: Error in as.character: cannot coerce type 'closure' to vector of type 'character'

This is the code I copied from Schmuller, Joseph. R Projects for Dummies, John Wiley & Sons, Incorporated, 2018. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/erau/detail.action?docID=5231273.

I have looked up answers on SO and have not found any successful fixes.

library(shiny)
library(shinydashboard)

ui <- dashboardPage( 
  dashboardHeader(title = "Sampling"),
  dashboardSidebar(
    sidebarMenu(
      menuItem("Uniform Distibution", 
               tabName = "uniform",
               icon = icon("circle")),
      menuItem("Normal Distribution",
               tabName = "normal",
               icon = icon("circle"))
    )),
  
  dashboardBody(
    tabItems(
     
       tabItem(
        tabName = "uniform",
        fluidRow(
          box(title = "Select a Number",
              solidHeader = TRUE, 
              background = "yellow", 
              status="warning", 
              height = 312, 
              sliderInput(inputId = "number",
                          label = "",
                          value = 500,
                          min = 25,
                          max = 1000)), 
          box(title = "Histogram",
              solidHeader=TRUE, 
              background = "light-blue", 
              status="primary", 
              plotOutput("hist", height = 250)),
          
          valueBoxOutput("meanBox"),
          valueBoxOutput("mediumBox"),
          valueBoxOutput("sdBox")
        )
      ),
      
      tabItem(
        tabName = "normal",
          fluidRow(
              box(title = "Select a Number",
                    solidHeader = TRUE,
                    collapsible = TRUE,
                    status = "warning",
                    sliderInput(inputId = "normnumber",
                                label = "",
                                value = 500,
                                min = 25,
                                max = 1000)),
                box(title = "Density Plot",
                    solidHeader = TRUE,
                    background = "light-blue",
                    status = "primary",
                    plotOutput("density", 
                               height = 250)),
                
                infoBoxOutput("meanInfoBox"),
                infoBoxOutput("medianInfoBox"),
                infoBoxOutput("sdInfoBox")
              )
      )
    ),
    
  ),
  
  
  server <- function(input, output) { 
    histdata <- {runif(input$number,min=0,max=1)}
    densitydata <- {rnorm(input$normnumber)}
    
    output$hist <- renderPlot({ 
      hist(histdata(),
           xlab="Value", 
           main=paste(input$number,
                      "random values between 0 and 1")) 
    }) 
    
    output$density <- renderPlot({
      hist(densitydata(),
           xlab="Value",
           main=paste("standard normal distribution \n",
                      input$normnumber,
                      "random values"),
           probability = TRUE)
      lines(density(densitydata()))
      
    output$meanBox <- renderValueBox({
        valueBox(
          round(mean(histdata()),3),
          "Mean",
          color = "navy"
        )
      })
      
      output$medianBox <- renderValueBox({
        valueBox(
          round(median(histdata()),3),
          "Median",
          color = "aqua"
        )
      })
      
      output$sdBox <- renderValueBox({
        valueBox(
          round(sd(histdata()),3),
          "Standard Deviation",
          color = "blue"
        ) 
      })
      
      output$meanInfoBox <- renderInfoBox({
        infoBox("Mean",
                round(mean(densitydata()),3),
                icon = icon("align-center"),
                color = "navy")
      })
      
      output$medianInfoBox <- renderInfoBox({
        infoBox("Median",
                round(median(densitydata()),3),
                icon = icon("area-chart"),
                color = "aqua")
      })
      
      output$sdInfoBox <- renderInfoBox({
        infoBox("Standard Deviation",
                round(sd(densitydata()),3),
                icon = icon("scribd"),
                fill = TRUE,
                color = "blue")
      })
    })
  }
)
shinyApp(ui, server)

I made a few changes to get this to work. See the modified code below. Usually, the UI and server are two separate functions, so I removed the comma before the server function.

Secondly, I made the data to be captured from the sliders "reactive", by wrapping the construction of histdata and densitydata in a reactive function (See first 2 lines in the server function). The reason here is that the data changes (or is regenerated) as you move the slider, so you have to instruct shiny to be dynamic in the same way (Run ?shiny::reactive in your console for help on this).

library(shiny)
library(shinydashboard)
ui <- dashboardPage(
dashboardHeader(title = "Sampling"),
dashboardSidebar(
sidebarMenu(
menuItem("Uniform Distibution",
tabName = "uniform",
icon = icon("circle")
),
menuItem("Normal Distribution",
tabName = "normal",
icon = icon("circle")
)
))
,
dashboardBody(
tabItems(
tabItem(
tabName = "uniform",
fluidRow(
box(title = "Select a Number",
solidHeader = TRUE,
background = "yellow",
status = "warning",
height = 312,
sliderInput(inputId = "number",
label = "",
value = 500,
min = 25,
max = 1000)
),
shinydashboard::box(title = "Histogram",
solidHeader=TRUE,
background = "light-blue",
status="primary",
plotOutput("hist", height = 250)
)
)
),
tabItem(
tabName = "normal",
fluidRow(
box(title = "Select a Number",
solidHeader = TRUE,
collapsible = TRUE,
status = "warning",
sliderInput(inputId = "normnumber",
label = "",
value = 500,
min = 25,
max = 1000
)
),
box(title = "Density Plot",
solidHeader = TRUE,
background = "light-blue",
status = "primary",
plotOutput("density",
height = 250
)
),
infoBoxOutput("meanInfoBox"),
infoBoxOutput("medianInfoBox"),
infoBoxOutput("sdInfoBox")
)
)
)
))
server <- function(input, output) {
histdata <- reactive({runif(input$number,min=0,max=1)})
densitydata <- reactive({rnorm(input$normnumber)})
output$hist <- renderPlot({
hist(histdata(),
xlab="Value",
main=paste(input$number,
"random values between 0 and 1")
)
})
output$density <- renderPlot({
hist(densitydata(),
xlab="Value",
main=paste("standard normal distribution \n",
input$normnumber,
"random values"),
probability = TRUE)
lines(density(densitydata()))
output$meanBox <- renderValueBox({
valueBox(
round(mean(histdata()),3),
"Mean",
color = "navy"
)
})
output$medianBox <- renderValueBox({
valueBox(
round(median(histdata()),3),
"Median",
color = "aqua"
)
})
output$sdBox <- renderValueBox({
valueBox(
round(sd(histdata()),3),
"Standard Deviation",
color = "blue"
)
})
output$meanInfoBox <- renderInfoBox({
infoBox("Mean",
round(mean(densitydata()),3),
icon = icon("align-center"),
color = "navy")
})
output$medianInfoBox <- renderInfoBox({
infoBox("Median",
round(median(densitydata()),3),
icon = icon("area-chart"),
color = "aqua")
})
output$sdInfoBox <- renderInfoBox({
infoBox("Standard Deviation",
round(sd(densitydata()),3),
icon = icon("scribd"),
fill = TRUE,
color = "blue")
})
})
}
shinyApp(ui, server)