Error "argument is of length zero"

[Iasmim Louriene]

Hey guys, I'm trying to run an App that makes the download of a plot in png or pdf file, but I once I click in the download button, it redirects me to a window with the following message
"argument is of length zero". Also, in the R console, I got the following:

Listening on http://127.0.0.1:3454
Error in if (input$var3 == "png") png(file) else pdf(file) :
argument is of length zero
Warning: Error in if: argument is of length zero
Stack trace (innermost first):
49: download$func [D:\Documents\Documents\Monografia\Tentativa_II_app_LiDAR\R_Shiny_Tutorial\Scripts\Tutorial 10/server.R#33]
1: runApp
Error in if (input$var3 == "png") png(file) else pdf(file) :
argument is of length zero
Warning: Error in if: argument is of length zero
Stack trace (innermost first):
49: download$func [D:\Documents\Documents\Monografia\Tentativa_II_app_LiDAR\R_Shiny_Tutorial\Scripts\Tutorial 10/server.R#33]
1: runApp

My script for server is this one:

library(shiny)
shinyServer(function(input,output)({

x <- reactive({
iris[,as.numeric(input$var1)]
})

y <- reactive({
iris[,as.numeric(input$var2)]
})


output$plot <- renderPlot({
plot(x(),y())
})

output$down <- downloadHandler(
#Specify the file name
filename = function(){
#iris.png
#iris.pdf
paste("iris", input$var3, sep=".")
},
content = function(file){
# open the device
#create the plot
#close the device
#png()
#pdf()

if(input$var3 == "png")
png(file)
else
pdf(file)
plot(x(),y())
dev.off()
}
)

}))

Does anyone have a clue about what could be done to solve this? Thanks a lot! :)

[Winston Chang]

The problem is probably that input$var3 is NULL or a zero-length vector. You can try print(input$var3) just above the line in question to see what the value is.

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[Joe Cheng]

And use req(input$var3), probably. http://shiny.rstudio.com/articles/req.html

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