Error: argument "expr" is missing, with no default - r

Question

So I'm trying to make a dashboard in R Shiny where in the first tab, users can input their data in csv file. And in the second tab they will see the summary and plot of their data. In the sub-tab Plot, the users will have to choose xlabel and ylabel from the dataset columns an the Plot A will show the scatter plot of xlabel and y label.
ui <- dashboardPage(skin='red',
dashboardHeader(title = "Dashboard"),
## Sidebar content
dashboardSidebar(
sidebarMenu(
menuItem("Data", tabName = "dashboard"),
menuItem("Visualization", tabName = "viz",
menuSubItem("Summary",tabName="sum"),
menuSubItem("Plot",tabName = "plot")),
menuItem("Interpretation", tabName = "int")
) ),
## Body content
dashboardBody(
tabItems(
# First tab content
tabItem(tabName = "dashboard",
fluidPage(titlePanel("DATA"),
fluidRow(
column(width=4,
fileInput("file1", "Input CSV file",
multiple = TRUE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",
".csv"))),
column(width=2,checkboxInput("header", "Header", TRUE)),
column(width=2,radioButtons("sep","Separator",
choices = c(Comma=",",
Semicolon = ";",
Tab = "\t"),
selected = ",")),
column(width=2,radioButtons("quote", "Quote",
choices = c(None = "",
"Double Quote" = '"',
"Single Quote" = "'"),
selected = '"')),
column(width=2,radioButtons("disp", "Display",
choices = c(Head = "head",
All = "all"),
selected = "head"))
),
tableOutput("contents")
)),
# Second tab content
tabItem(tabName = "sum",
box(
title="Summary",
status="primary",
solidHeader = TRUE,
width = "100%",
collapsible = TRUE,
verbatimTextOutput("summary")
)
),
tabItem(tabName="plot",
h2("Plot"),
fluidRow(
selectInput("sip","select",choices = 1:10),
selectInput("sila","anda",choices = 1:10)
),
fluidRow(
box(
title = "Plot A",
status= "primary",
solidHeader = TRUE,
collapsible = TRUE,
plotOutput("plota",height="300px")
),
box(
title = "Plot B",
status= "primary",
solidHeader = TRUE,
collapsible = TRUE,
plotOutput("plotb",height="300px"
)
)
)),
tabItem(tabName = "int",
h2("hello")
)
)
))
server <- function(input, output,session) {
output$contents <- renderTable({
# input$file1 will be NULL initially. After the user selects
# and uploads a file, head of that data file by default,
# or all rows if selected, will be shown.
req(input$file1)
df <- read.csv(input$file1$datapath,
header = input$header,
sep = input$sep,
quote = input$quote)
if(input$disp == "head") {
return(head(df))
}
else {
return(df)
}
})
output$summary <- renderPrint({
req(input$file1)
dataset<- read.csv(input$file1$datapath,
header = input$header,
sep = input$sep,
quote = input$quote)
summary(dataset)
})
output$plota <- renderPlot({
req(input$file1)
dataset<- read.csv(input$file1$datapath,
header = input$header,
sep = input$sep,
quote = input$quote)
updateSelectInput(session,"sip",label="label",choices=names(dataset))
updateSelectInput(session,"sila",label="label",choices = names(dataset))
plot(dataset[eventReactive(input$sip)],dataset[eventReactive(input$sila)],pch=19)
})
output$plotb <- renderPlot({
})
}
shinyApp(ui, server)
This is how the code looks like. When i run this program, it result in error: argument "expr" is missing, with no default. What is expr in this context?

Answer 1

You don't need to use eventReactive since renderPlot is a reactive expression, use only the input$..
Another problem is that you are trying to update the selectImput's inside the renderPlot, which is not going to work. You should update them with a different reactive expression, like a reactive() where you can also read the file instead of reading it multiple times. Below is your code modified to solve the problem and also reading the file only once inside a reactive expression.
library(shiny)
library(shinydashboard)
ui <- dashboardPage(skin='red',
dashboardHeader(title = "Dashboard"),
## Sidebar content
dashboardSidebar(
sidebarMenu(
menuItem("Data", tabName = "dashboard"),
menuItem("Visualization", tabName = "viz",
menuSubItem("Summary",tabName="sum"),
menuSubItem("Plot",tabName = "plot")),
menuItem("Interpretation", tabName = "int")
) ),
## Body content
dashboardBody(
tabItems(
# First tab content
tabItem(tabName = "dashboard",
fluidPage(titlePanel("DATA"),
fluidRow(
column(width=4,
fileInput("file1", "Input CSV file",
multiple = TRUE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",
".csv"))),
column(width=2,checkboxInput("header", "Header", TRUE)),
column(width=2,radioButtons("sep","Separator",
choices = c(Comma=",",
Semicolon = ";",
Tab = "\t"),
selected = ",")),
column(width=2,radioButtons("quote", "Quote",
choices = c(None = "",
"Double Quote" = '"',
"Single Quote" = "'"),
selected = '"')),
column(width=2,radioButtons("disp", "Display",
choices = c(Head = "head",
All = "all"),
selected = "head"))
),
tableOutput("contents")
)),
# Second tab content
tabItem(tabName = "sum",
box(
title="Summary",
status="primary",
solidHeader = TRUE,
width = "100%",
collapsible = TRUE,
verbatimTextOutput("summary")
)
),
tabItem(tabName="plot",
h2("Plot"),
fluidRow(
selectInput("sip","select",choices = 1:10),
selectInput("sila","anda",choices = 1:10)
),
fluidRow(
box(
title = "Plot A",
status= "primary",
solidHeader = TRUE,
collapsible = TRUE,
plotOutput("plota",height="300px")
),
box(
title = "Plot B",
status= "primary",
solidHeader = TRUE,
collapsible = TRUE,
plotOutput("plotb",height="300px"
)
)
)),
tabItem(tabName = "int",
h2("hello")
)
)
))
server <- function(input, output,session) {
dataset <- reactive({
req(input$file1)
dat <- read.csv(input$file1$datapath,
header = input$header,
sep = input$sep,
quote = input$quote)
updateSelectInput(session,"sip",choices=names(dat))
updateSelectInput(session,"sila",choices = names(dat))
dat
})
output$contents <- renderTable({
# input$file1 will be NULL initially. After the user selects
# and uploads a file, head of that data file by default,
# or all rows if selected, will be shown.
req(input$file1)
df <- dataset()
if(input$disp == "head") {
return(head(df))
}
else {
return(df)
}
})
output$summary <- renderPrint({
req(input$file1)
summary(dataset())
})
output$plota <- renderPlot({
plot(dataset()[[input$sip]],dataset()[[input$sila]],pch=19)
})
output$plotb <- renderPlot({
})
}
shinyApp(ui, server)