if else in shiny reactive - r

Question

I have a rather simple problem but can not figure out why it is not working
library(shiny)
library(leaflet)
pts <- data.frame(
id = letters[seq(from = 1, to = 10)],
x = rnorm(10, mean = -93.625),
y = rnorm(10, mean = 42.0285),
stringsAsFactors = F
)
# Define UI
ui <- fluidPage(uiOutput('Select'))
server <- function(input, output, session) {
pts
output$Select <- renderUI({
Range <- sort(unique(pts$id))
selectInput("dataselect",
"select",
choices = Range,
selected = 'a')
})
mydata <- reactive({
if (input$dataselect != 'a') {
data <- pts[pts$id == input$dataselect,]
}
else
{
data <- pts
}
})
observe(print(mydata()))
}
shinyApp(ui = ui, server = server)
I basically try to subset my data set if anything else than 'a' is selected with the selected value. If 'a' is selected I want the whole df returned.
Just run into
Warning: Error in if: argument is of length zero [No stack trace
available]

Answer 1

You need to to not run mydata() if input$dataselect is not available, that can be done by inserting: req(input$dataselect)
As shown below:
library(shiny)
library(leaflet)
pts <- data.frame(
id = letters[seq(from = 1, to = 10)],
x = rnorm(10, mean = -93.625),
y = rnorm(10, mean = 42.0285),
stringsAsFactors = F
)
# Define UI
ui <- fluidPage(uiOutput('Select'))
server <- function(input, output, session) {
output$Select <- renderUI({
Range <- sort(unique(pts$id))
selectInput("dataselect",
"select",
choices = Range,
selected = 'a')
})
mydata <- reactive({
req(input$dataselect)
if (input$dataselect != 'a') {
data <- pts[pts$id == input$dataselect,]
}
else
{
data <- pts
}
})
observe(print(mydata()))
}
shinyApp(ui = ui, server = server)