how to extract numericInput() value and use it as integer?

[ahmedshingaly]

i am doing some simple calculations using R and presenting them in shiny where some variables of the calculations should be inserted by the user.

in the ui <-
I have
Q1 <- numericInput("myInput1", "question1", value= 1)

I want to extract the Q1 numeric integer value which in this case number 1 and use it in another equation, for example:

B= Q1+1

the Q1 is a numericInput inside shiny ui and a user could change the value by typing a different value ex: number 2 . the new value should be used to calculate Q1 value which is 2 + 1 = 3 the value of B

when I run the app, I face this error message:
Error in Q1 + 1 : non-numeric argument to binary operator

thank you in advance for looking at my problem and appreciate your help

thanks
Ahmed Ali
PhD candidate
Chung Ang University

[FJCC]

The value of the numericInput is part of the input list, You refer to it with its inputId, myInput1, as input$myInput1. Here is a very simple example. Note that the calculations are done in the server section of the app.

library(shiny)

ui <- fluidPage(
  titlePanel("Title"),
  mainPanel(
    numericInput("myInput1", label = "Number", value = 1),
    plotOutput("Plot")
  )
)

server <- function(input, output) {
  output$Plot <- renderPlot({
    Yvals <- seq(from = input$myInput1, to = input$myInput1 *2, length.out = 5) 
    plot(1:5, Yvals)
  })
    
}


shinyApp(ui = ui, server = server)

[ahmedshingaly]

thanks alot for your quick reply,
so in the below example:
in ui<-
user insert "myInput1" value then
in server<- B = input$myInput1+2

my questions is: how can I use the "B" value as integer in further integer calculations. for example: I want to use B+2= C then C+2=D finally print D as final result in shiny?

concept in shiny: user insert myInput1 value and get the result of D

library(shiny)

ui <- fluidPage(
titlePanel("Title"),
mainPanel(
numericInput("myInput1", label = "Number", value = 1),
uiOutput("ui")
)
)

server <- function(input, output) {

output$ui <- renderUI( {
tagList(
tags$h2("Display Result in %"),
numericInput("obs1", "B", value = input$myInput1+2))
})
}

shinyApp(ui = ui, server = server)

[FJCC]

If you just want to display the result of a calculation, you can use renderUI as shown below.

library(shiny)

ui <- fluidPage(
  titlePanel("Title"),
  mainPanel(
    numericInput("myInput1", label = "Number", value = 1),
    uiOutput("ui"),
    uiOutput("ui2")
  )
)

server <- function(input, output) {

  
  output$ui <- renderUI( {
    tagList(
      tags$h2("Display Result in %"),
      numericInput("obs1", "B", value = input$myInput1+2))
  })
  output$ui2 <- renderUI({
    C <- input$myInput1 + 2
    D <- C^2
    tags$div(paste("The processed input is", D))
  })
}

shinyApp(ui = ui, server = server)

[ahmedshingaly]

Dear FJCC
thanks alot. that solved the problem

have a blessed day