multiple selectizeInput from fileInput - file-io

Question

I would like to have a user input a file (.csv) and from that file, two selectizeInputs will populate with the column names of the .csv. One will ask the user which of the columns from their uploaded file is the y-variable and which of the columns is the x-variable. This, I was able to do.
What I cannot do is the following: I would like to get the selection from their y-variable to disappear from their x-variable choices in the x-variable drop-down menu.
Also, I've used the answer to this question to try to help, but they are not using the values from a fileInput. As such, I cannot get my code, which is below, to work. Thank you for any advice/help you can give.
ui<- fluidPage(
titlePanel("Test"),
sidebarPanel(
fileInput(inputId = "file1", label = "Upload File"),
selectizeInput(
"sampleyvars", "Y-vars", choices = NULL, multiple = FALSE
),
selectizeInput(
"samplevars", "X-vars", choices = NULL, multiple = TRUE
)
),
mainPanel(h3("Nothing special")
)
)
server<- function(input, output, session) {
observe({
file1 <- input$file1
if(is.null(file1)){return()}
dataSet <- read.csv(file=file1$datapath)
vals1<-input$sampleyvars
vals2<-input$samplevars
updateSelectizeInput(session, "sampleyvars",
choices = colnames(dataSet)[! vals1 %in% vals2])
updateSelectizeInput(session, "samplexvars",
choices =colnames(dataSet)[! vals2 %in% vals1])
})
}
shinyApp(ui = ui,server = server)

Answer 1

You had wrong ID of the widget for X variable: samplevars instead of samplexvars which you used in update* function. I changed it to the latter ID and also slightly tweaked your code to get the desired effect.
Full example:
ui<- fluidPage(
titlePanel("Test"),
sidebarPanel(
fileInput(inputId = "file1", label = "Upload File"),
selectizeInput(
"sampleyvars", "Y-vars", choices = NULL, multiple = FALSE
),
# you had ID here wrong
selectizeInput(
"samplexvars", "X-vars", choices = NULL, multiple = TRUE
)
),
mainPanel(h3("Nothing special")
)
)
server<- function(input, output, session) {
data <- reactive({
file1 <- input$file1
req(file1)
dataSet <- read.csv(file=file1$datapath)
vars <- colnames(dataSet)
updateSelectizeInput(session, "sampleyvars", "Y-vars",
choices = vars, selected = vars[1])
updateSelectizeInput(session, "samplexvars", choices = vars[-1], selected = vars[2])
dataSet
})
observe({
varX <- colnames(data())
varX <- varX[!(varX %in% input$sampleyvars)]
updateSelectizeInput(session, "samplexvars", "X-vars", choices = varX)
})
}
shinyApp(ui = ui,server = server)