CODEWITHSUNDEEP
rshinyshiny-server
Jack F
Jack F

Reputation: 3

R Shiny: How to create server-side functions that paste "input$" with function argument inputs

I am trying to create a function to simplify a long reactive expression. The goal is to create a data frame out of user-inputs. The goal of the function is to dynamically refer to different inputs in the UI based on the function argument. The function has a "day" argument which should be pasted with input$A to create input$A<day> where <day> is an input to my server-side function. In the below example, I would run foo(day = 1) in my main server function, which would create a dataframe out of the inputs the user entered into "Day 1" of my app.

I very naively started with:

foo <- function(day) {
     df <- data.frame(
         "A"     = paste0("input$A", day),
         "B"     = paste0("input$B", day)
     )
}

I understand this won't work and just creates a dataframe with rows of text saying "input$Aday" and "input$Bday". I have since explored using eval(parse()), rlang, etc and have not gotten this to work. Any help would be greatly appreciated.

Upvotes: 0

Views: 1085

Answers (1)

jpdugo17
jpdugo17

Reputation: 7106

Here are two ways to refer to the input as an object:

library(tidyverse)
library(shiny)

ui <- fluidPage(
  textInput('A1', 'InputA1', value = 'hello'),
  textInput('B1', 'InputB1', value = 'How are you?')
)

server <- function(input, output, session) {
  
    foo1 <- function(day) {
        df <- data.frame(
            "A"     = input[[str_c('A', day)]],
            "B"     = input[[str_c("B", day)]]
        )
    }
    
    foo2 <- function(day) {
        df <- tibble(
            "A"     = parse(text =str_c('input$A', day)) %>% eval(),
            "B"     = parse(text =str_c('input$B', day)) %>% eval()
        )
    }
    
    observe({
        print(foo1(day = 1))
        print(foo2(day = 1))})
    
    
}

shinyApp(ui, server)
#> 
#> Listening on http://127.0.0.1:6240
#>       A            B
#> 1 hello How are you?
#> # A tibble: 1 x 2
#>   A     B           
#>   <chr> <chr>       
#> 1 hello How are you?

Created on 2021-06-26 by the reprex package (v2.0.0)

Upvotes: 1

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