R Shiny won't output a variable using textOutput - r

Question

I'm trying to write a calculator using Shiny in R for a video game (you input the stats of you and your opponent, and it outputs your odds of winning a match). However, I can't get the Shiny app to output any of my variables. The app runs fine, but nothing outputs when the action button is selected.
Trying to find the issue, I simplified my code into a basic calculator that takes a numeric input, multiplies it by two, and outputs a result. As before, nothing is displayed when the action button is pushed. However, if you directly type a string into the renderText function, it works just fine.
I need to include an action button in my ultimate code because I don't want it to calculate the result until several numerical values have been typed in. Could the action button be causing an issue somewhere, or is it something else?
Below is the simplified code. If I can get this to run, I'm sure I could get my more complicated code to run. Thank you!
library(shiny)
library(shinythemes)
ui <- fluidPage(
titlePanel("Multiply by 2"),
fluidRow(
column(12, textOutput("test"),
numericInput(inputId = "start", "Start", value = 1),
actionButton("go", "Go!") )
)
)
server <- function(input, output) {
myval <- reactiveValues()
observeEvent(input$go, {
reactive ({
if (input$go == 0)
return()
isolate({
myval$calc <- paste("The result is", 2*input$start)
})
})
})
output$test <- renderText({
if (input$go == 0)
return()
isolate({
myval$calc
})
})
}
shinyApp(ui = ui, server = server)

Answer 1

It looks like there is some extra code in there we don't need, for example the isolate function. See the below minimal example:
input$go doesn't tell us what the button is doing. Try running print(input$go) and have a look at the output.
library(shiny)
ui <- fluidPage(
titlePanel("Multiply by 2"),
fluidRow(
column(12,
textOutput("test"),
numericInput(inputId = "start", "Start", value = 1),
actionButton("go", "Go!")
)
)
)
server <- function(input, output) {
myval <- reactiveValues()
#Observe button (will run when the button is clicked)
observeEvent(input$go, {
myval$calc <- paste("The result is", 2 * input$start)
})
#Text output (will run when myval$calc changes)
output$test <- renderText({
myval$calc
})
}
shinyApp(ui = ui, server = server)