Struggling in getting output in r shiny app - r

Question

I'm a beginner in shiny app. so first I tried to build an app to calculate distance covered using time taken and speed. I got error as "argument of length zero". Then I entered req(input$num_time,input$select_time,input$slider_speed)this command after that error message is not displaying and also not getting output also. I'm not able to find where I gone wrong. Please help me in getting the output. I have shown the code I used below:
library(shiny)
#library(car)
ui <- fluidPage(
titlePanel("terrain model"),
sidebarLayout(
sidebarPanel(
helpText("To create a suitable model"),
br(),
numericInput("num_time",
label = h6("Enter time"),
value = 1),
selectInput("select_time",
label = h6(""),
choices = list("Hours"= 1,"Minutes" = 2),
selected = "1"),
sliderInput("Speed",
label = "Speed:",
min = 2, max = 4.5, value = 2),
br(),
actionButton("action",label="Refresh & Calculate")
),
mainPanel(
textOutput("text_distance")
)
)
)
server <- function(input, output) {
values <- reactiveValues()
#calculate distance travelled
observe({input$action_Calc
values$int <- isolate({ input$num_time * recode(input$select_time,"1='60';2='1'")*input$slider_speed
})
})
#Display values entered
output$text_distance <- renderText({
req(input$num_time,input$select_time,input$slider_speed)
if(input$action_Calc==0)""
else
paste("Distance:", round(values$int,0))
})
}
shinyApp(ui, server)

Answer 1

I don't find any use of "Refresh & Calculate" button since the calculation is performed as soon as any of the input changes.
You can try this code :
ui <- fluidPage(
titlePanel("terrain model"),
sidebarLayout(
sidebarPanel(
helpText("To create a suitable model"),
br(),
numericInput("num_time",
label = h6("Enter time"),
value = 1),
selectInput("select_time",
label = h6(""),
choices = list("Hours"= 1,"Minutes" = 2),
selected = "1"),
sliderInput("Speed",
label = "Speed:",
min = 2, max = 4.5, value = 2),
br(),
actionButton("action",label="Refresh & Calculate")
),
mainPanel(
textOutput("text_distance")
)
)
)
server <- function(input, output) {
#Display values entered
output$text_distance <- renderText({
val <- input$num_time/dplyr::recode(input$select_time,"1"=1,"2"=60)*input$Speed * 1000
paste("Distance:", round(val,0), 'meters')
})
}
shinyApp(ui, server)