Update two sets of radiobuttons reactively - shiny - r

Question

I have read this (How do I make the choices in radioButtons reactive in Shiny?) which shows me how to update radioButtons in a reactive way. However, when I try and update two sets of buttons from the same data, only one set renders. Example:
Server:
# Create example data
Wafer <- rep(c(1:3), each=3)
Length <- c(1,1,2,1,1,1,3,5,1)
Width <- c(3,1,6,1,1,1,1,1,6)
dd <- data.frame(Wafer, Length, Width)
shinyServer(function(input, output, session){
# Create reactive dataframe to store data
values <- reactiveValues()
values$df <- data.frame()
# Get Lengths and Widths of wafer from user input
a <- eventReactive(input$do, {
subset(dd, Wafer %in% input$wafer, select = Length:Width)
})
# Update reactive data frame will all Lengths and Widths that have been selected by the user input
observe({
if(!is.null(a())) {
values$df <- rbind(isolate(values$df), a())
}
})
output$wl <- renderDataTable({ a() })
# Update radio buttons with unique Length and Widths stored in values$df
# Which ever "observe" I put first in the code, is the one which updates
# the radio buttons. Cut and paste the other way round and "width"
# updates but not "length" radio buttons
observe({
z <- values$df
updateRadioButtons(session, "length", choices = unique(z$Length), inline=TRUE)
})
observe({
z <- values$df
updateRadioButtons(session, "width", choices = unique(z$Width), inline=TRUE)
})
})
ui:
library(markdown)
shinyUI(fluidPage(
titlePanel("Generic grapher"),
sidebarLayout(
sidebarPanel(
numericInput("wafer", label = h3("Input wafer ID:"), value = NULL),
actionButton("do", "Search wafer"),
radioButtons("length", label="Length", choices=""),
radioButtons("width", label="Width", choices = "")
),
mainPanel(
dataTableOutput(outputId="wl")
)
)
)
)
In the above, radiobuttons do update but only for the first set of buttons in order of code i.e. above "length" updates but "width" doesn't. If I write them in reverse, "width" updates but "length" doesn't. Do I need to define a new session maybe?

Answer 1

It turns out that:
"it's because a JS error occurs if the choices argument isn't a
character vector."
I have posted an issue on Shiny's Github:
https://github.com/rstudio/shiny/issues/1093
This can be resolved by:
To fix your problem, you can either convert your choices to characters
using as.character or set selected to a random string such as "".
See:
Update two sets of radiobuttons - shiny