5.10 Tracebacks in Shiny
You can’t use
traceback()in Shiny because you can’t run code while an app is running.Shiny automatically prints the traceback for you.
library(shiny)
f <- function(x) g(x)
g <- function(x) h(x)
h <- function(x) x * 2
ui <- fluidPage(
selectInput("n", "N", 1:10),
plotOutput("plot")
)
server <- function(input, output, session) {
output$plot <- renderPlot({
n <- f(input$n)
plot(head(cars, n))
}, res = 96)
}
shinyApp(ui, server)- We will see an error below
Error in *: non-numeric argument to binary operator
169: g [app.R#4]
168: f [app.R#3]
167: renderPlot [app.R#13]
165: func
125: drawPlot
111: <reactive:plotObj>
95: drawReactive
82: renderFunc
81: output$plot
1: runApp- We can also flip the error