Using numeric input in shiny app yields a "Error: object 'input' not found"

Question

I have a very simple shiny app that is makes a gt table using some inputs.

One of my goals is to pass a user input which is numeric into the cols_width() argument so I can add padding to my first column. Although when doing something like the following I get an error that the input is not found.

  output$table <- render_gt( 
    reactive_tab() %>% 
      gt() %>% 
      cols_width(
        1 ~ px(input$colpad)
      )
  )

I've also tried doing {input$colpad} and .(input$colpad) with no success either.

Desired Output:

Here is the code:

library(data.table)
library(shiny)
library(gt)
library(shinyscreenshot)

data <- gtcars %>% head(10) %>% 
  select(mfr, model, msrp)

ui <- navbarPage("Y u no pad??",
                 tabPanel("Table", icon = icon("table"),
                          
                          sidebarLayout(
                            sidebarPanel(
                              selectInput("input",
                                          label = "Choose mfr",
                                          choices = c("All", data$mfr)),
                              numericInput("colpad", label = "First Column Padding", min = 1, max = 10000, value = 150),
                              screenshotButton(selector="#table", label = 'Download Png', filename = 'screenshot'),
                            ),
                            
                            mainPanel(
                              gt_output("table")
                            )
                          )
                 )
)



server <- function(input, output, session) {
  
  reactive_tab  <- reactive({
    d <- data
    if(input$input != "All")
      d <- subset(d, cyl == input$input)
    d 
  })
  
  output$table <- render_gt( 
    reactive_tab() %>% 
      gt() %>% 
      cols_width(
        1 ~ px(input$colpad)
      )
  )
  
  

}
shinyApp(ui, server)

Hmm. I looked it and although it’s closed. There doesn’t really seem like a clear solution? Any thoughts? Thank you for the link — RL_Pug
– RL_Pug, Commented Jul 2, 2022 at 2:16

the-mad-statter · Accepted Answer · 2022-07-05 17:42:54Z

Reason

The reason this is not working is because of the way gt::cols_width() evaluates is arguments. It does not know which environment to look in to find the input object.

One way to circumvent the issue is to first evaluate input$colpad and then pass the value in a way gt::cols_width() will understand.

Code

Here is one such approach where I paste together a formula and cast it as such on line 46:

library(data.table)
library(shiny)
library(gt)
library(shinyscreenshot)
select <- dplyr::select

data <- gtcars %>%
  head(10) %>%
  select(mfr, model, msrp)

ui <- navbarPage(
  "Y u no pad??",
  tabPanel("Table",
    icon = icon("table"),
    sidebarLayout(
      sidebarPanel(
        selectInput("input",
          label = "Choose mfr",
          choices = c("All", data$mfr)
        ),
        numericInput("colpad", label = "First Column Padding", min = 1, max = 10000, value = 150),
        screenshotButton(selector = "#table", label = "Download Png", filename = "screenshot"),
      ),
      mainPanel(
        gt_output("table")
      )
    )
  )
)



server <- function(input, output, session) {
  reactive_tab <- reactive({
    d <- data
    if (input$input != "All") {
      d <- subset(d, cyl == input$input)
    }
    d
  })

  output$table <- render_gt(
    reactive_tab() %>%
      gt() %>%
      cols_width(
        as.formula(paste0("1 ~ ", input$colpad)) # EDIT HERE
      )
  )
}



shinyApp(ui, server)

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