Subsetting dataframe based on dynamically generated checkBoxGroupInput: checkbox keeps resetting - r

Question

I would like to use a Shiny app to load a file (tab-separated), dynamically create a checkboxGroupInput, after the loading of the file (using observeEvent) using the column headers, then subset the data frame that comes from the file based on the selected checkboxes. The data is then plotted using code I can't share right now.
All is working fine, apart from the last bit: subsetting the dataframe based on the selected checkboxes in checkboxGroupInput. The checkboxes all start selected, and the plot is created fine. If you un-select one of the checkboxes, the plot re-plots appropriately for a split second (so the subsetting is working fine) then the unselected checkbox re-selects itself and the plot goes back to the old plot.
This is the tiny problem I'm trying to solve, guessing it's one line of code. I'm assuming it's because of some reactivity that I don't understand and the checkbox constantly resetting itself.
Here is an example:
###
## Some functions I can't share
### Shiny app
library(shiny)
# Define UI
ui <- fluidPage(
# Application title
titlePanel("MagicPlotter"),
# Sidebar
sidebarLayout(
sidebarPanel(
fileInput(inputId = "myInputID",
label = "Your .csv file",
placeholder = "File not uploaded"),
uiOutput("mylist"),
uiOutput("submitbutton")
),
# Show a plot
mainPanel(
verticalLayout(
plotOutput("myPlot"))
)
)
)
# Define server
server <- function(input, output) {
output$myPlot <- renderPlot({
inputfile <- input$myInputID
if(is.null(inputfile))
{return()}
mydataframe <- read.table(file=inputfile$datapath, sep="\t", head=T, row.names = 1)
mydataframecolumnnames <- colnames(mydataframe[1:(length(mydataframe)-1)])
# the last column is dropped because it's not relevant as a column name
observeEvent(input$myInputID, {
output$mylist <- renderUI({
checkboxGroupInput(inputId="mylist",
label="List of things to select",
choices=mydataframecolumnnames,
selected=mydataframecolumnnames)
})
})
observeEvent(input$myInputID, {
output$submitbutton <- renderUI({
submitButton("Subset")
})
})
mysubset <- mydataframe[input$mylist]
myPlot(mysubset)
})
}
# Run the application
shinyApp(ui = ui, server = server)
Thanks all

Answer 1

I think there are a few things that might help...
One, you can move your observeEvent methods outside of your renderPlot.
Also, you can create a reactive function to read in the data table.
I hope this helps.
server <- function(input, output) {
myDataFrame <- reactive({
inputfile <- input$myInputID
if(is.null(inputfile))
{return()}
read.table(file=inputfile$datapath, sep="\t", head=T, row.names = 1)
})
output$myPlot <- renderPlot({
req(input$mylist)
mysubset <- myDataFrame()[input$mylist]
plot(mysubset)
})
observeEvent(input$myInputID, {
mydata <- myDataFrame()
mydataframecolumnnames <- colnames(mydata[1:(length(mydata)-1)])
output$mylist <- renderUI({
checkboxGroupInput(inputId="mylist",
label="List of things to select",
choices=mydataframecolumnnames,
selected=mydataframecolumnnames)
})
})
observeEvent(input$myInputID, {
output$submitbutton <- renderUI({
submitButton("Subset")
})
})
}