Shiny Selectinput for every non-numeric column of a Filteinput data - r

Question

I would like to create a Shiny dashboard where:
1) The user selects an excel file
2) A Selectinput option is created for every non-numeric column of the obtained dataframe is created that gives users the option to select every unique value in this column. This is how my code looks so far:
library(shiny)
library(dplyr)
library(openxlsx)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
fileInput('datafile', 'Choose xlsx file',
accept = c(".xlsx")),
lapply(names("varselect"), function(i) {
selectInput(paste0(i), paste0(i),
choices = "varselect"[i],
multiple = TRUE,
selected = "")})),
mainPanel()))
server <- function(input, output,session) {
Data <- reactive({
infile <- input$datafile
if (is.null(infile)) {
return(data.frame())
}
read.xlsx(infile$datapath,
sheetIndex = 1) %>% select_if(colSums(!is.na(.)) > 0%>% select_if(~!is.numeric(.x)) %>% head())
})
output$varselect <- renderUI({
})
observe({
lapply(names(Data()), function(i) {
selectInput(paste0(i), paste0(i),
choices = Data()[i],
multiple = TRUE,
selected = "")})})
}
shinyApp(ui = ui, server = server)
I am aware of the fact that the code is not working and that there are some grave mistakes, but I hope that somebody can help me to find an approach that does work for this problem. I am rather new to Shinny and that is why i honestly have no clue how to solve this problem.
Many thanks.

Answer 1

In your ui, you can include a uiOutput which will contain all of the dynamically created selectInput widgets.
Then, in output$varselect you can create the selectInput based on the number of columns in Data().
library(shiny)
library(dplyr)
library(openxlsx)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
fileInput('datafile', 'Choose xlsx file',
accept = c(".xlsx")),
uiOutput("varselect")
),
mainPanel()
)
)
server <- function(input, output, session) {
Data <- reactive({
infile <- input$datafile
if (is.null(infile)) {
return(data.frame())
}
read.xlsx(infile$datapath, sheet = 1) %>%
select_if(colSums(!is.na(.)) > 0) %>%
select_if(~!is.numeric(.x)) %>%
head()
})
output$varselect <- renderUI({
if (ncol(Data() > 0)) {
lapply(1:ncol(Data()), function(i) {
selectInput(inputId = paste0("si_", i),
label = paste0("Input #", i),
choices = Data()[,i],
multiple = TRUE)
})
}
})
}
shinyApp(ui = ui, server = server)