How to use a user-written function within a shiny app?

Question

I'm trying to get a function work within a shiny app, but it doesn't work as expected. Outside of the app it works fine,

But within the app, it doesn't work:

Is it because the input$var isn't working as expected? (The checkbox also doesn't work and I'm still trying to figure that out.) My main question is about the function.

Code:

library(shiny)
if (interactive()) {
  
  one <- function(.data, var, na = TRUE) {
  
  if (na == FALSE)
  
    return({
  .data %>% 
    group_by({{var}}) %>% 
    drop_na() %>% 
    tally() %>% 
    mutate(`%` = 100*n/sum(n))
      
    })
  
  if (na == TRUE)
    return({
  
  .data %>% 
    group_by({{var}}) %>% 
  #  drop_na() %>% 
    tally() %>% 
    mutate(`%` = 100*n/sum(n))
      
    })
  
}

ui <- fluidPage(
  selectInput("var", label = "Select Variable", choices = c(" ", names(mtcars))),
  checkboxInput("check", "Display missing", FALSE),
  tableOutput("value")
)
server <- function(input, output) {
  output$value <- renderTable({ 
    
    req(input$var)
    if (input$check) ({
    mtcars %>% 
      one(input$var, na = TRUE)
    
    }) 
    
    if(!input$check) ({
      mtcars %>% 
      one(input$var, na = FALSE)
    })
    
    
  })
}
shinyApp(ui, server)
}

Dataset with missing values:

df <- data.frame(col1 = c(1:3, NA),
                 col2 = c("this", NA,"is", "text"), 
                 col3 = c(TRUE, FALSE, TRUE, TRUE), 
                 col4 = c(2.5, 4.2, 3.2, NA),
                 stringsAsFactors = FALSE)

Ronak Shah · Accepted Answer · 2021-01-03 03:11:44Z

input$var is a character value whereas one function is written for unquoted variables. You can change your function to work for character values.

Other changes that I did in the code are -

Replace na == FALSE and na == TRUE to !na and na respectively.
Since you want to keep the first value in selectInput as blank, used if(input$var != '') instead of req(input$var) because input$var would always have a value.

library(shiny)
library(dplyr)

if (interactive()) {
  
  one <- function(.data, var, na = TRUE) {
    if (!na)
      return({
        .data %>% 
          group_by(.data[[var]]) %>% 
          filter(!is.na(.data[[var]])) %>%
          tally() %>% 
          mutate(`%` = 100*n/sum(n))
        
      })
    
    if (na)
      return({
        
        .data %>% 
          group_by(.data[[var]]) %>% 
          tally() %>% 
          mutate(`%` = 100*n/sum(n))
      })
    
  }
  
  ui <- fluidPage(
    selectInput("var", label = "Select Variable", choices = c("", names(df))),
    checkboxInput("check", "Display missing", FALSE),
    tableOutput("value")
  )
  server <- function(input, output) {
    output$value <- renderTable({ 
      
      if(input$var != '') {
        data <- df %>% one(input$var, na = input$check)
        return(data)
      }
    })
  }
  shinyApp(ui, server)
}

YBS · Accepted Answer · 2021-01-03 13:27:54Z

Use get() to accomplish your needs. Also, you can use .data[[!!input$var]] to get the appropriate name in the header of the displayed table.

  one <- function(.data, var, na = TRUE) {

    if (na == FALSE)

      return({
        .data %>%
          group_by({{var}}) %>%
          filter(!is.na({{var}})) %>%
          tally() %>%
          mutate(`%` = 100*n/sum(n))

      })

    if (na == TRUE)
      return({

        .data %>%
          group_by({{var}}) %>%
          #  drop_na() %>%
          tally() %>%
          mutate(`%` = 100*n/sum(n))

      })

  }

  ui <- fluidPage(
    selectInput("var", label = "Select Variable", choices = c(" ",names(mtcars))),
    checkboxInput("check", "Display missing", FALSE),
    tableOutput("value")
  )
  server <- function(input, output) {
    output$value <- renderTable({
      if (!is.null(input$var)) {
        if (input$var == " " | is.na(input$var)) {
          df <- mtcars  ## choose what you want to display when input$var is missing; NULL if you want to show nothing
        }else {
          df <- mtcars %>%   one(.data[[!!input$var]], na = req(input$check))
        }
        
      }else df <- NULL
      df
    })
  }
  shinyApp(ui, server)

Collectives™ on Stack Overflow

How to use a user-written function within a shiny app?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related