How to restart an lapply loop within a renderUI - r

Question

I am trying to create a shiny code that is able to filter a table non pre-determined number of times. When the user uploads a different (new) table, unfortunately the code breaks as I need to restart a lapply loop somehow, throwing out the previously stored column names.
I would like to create an non pre-defined filtering options for a table within Shiny. The user can select a column and filter a table choosing different categorical variables within that column. It is possible to add additional selection fields by pressing the 'Add' button.
the UI:
library(shiny)
library(shinydashboard)
library(dplyr)
ui <- shinyUI(
pageWithSidebar(
headerPanel("testing of dynamic number of selection"),
sidebarPanel(
uiOutput("buttons")),
mainPanel(
uiOutput("drops")
,tableOutput("table")
)
))
The server:
A table (test.csv) is automatically stored in a reactive values and a first searching field appears with 3 buttons (Add = to add a new searching field by reading in the colnames and a multiselect that stores the unique variables from that columns. The filtering function is activated by the Calculate button)
server<-function(input, output, session) {
###### read in test file
values<-reactiveValues(number = 1,
upload = NULL,
input = NULL)
values$upload<-read.csv("test.csv")
#just the "add" button, in this instance it shouldn't be a uiOutput
output$buttons <- renderUI({
div(
actionButton(inputId = "add", label = "Add"), actionButton(inputId = "calc", label = "Calculate"),
actionButton(inputId = "new", label = "new table")
)
})
#pressing the add button
observeEvent(input$add, {
cat("i adding a new record\n")
values$number <- values$number + 1L })
daStuff <- function(i){
inputName<-paste0("drop", i)
inputName2<-paste0("select", i)
inputText<-if(values$number>0){input[[paste0("drop",i)]]}else{F} # previously selected value for dropdown
inputSelect <- if(values$number>1){input[[paste0("select",i)]]}else{F} # previously selected value for dropdown
fluidRow(
column(6,selectInput(inputName, inputName, c(colnames(values$upload)), selected = inputText)),
column(6,selectInput(inputName2, inputName2,
na.omit(unique(as.vector(values$upload[,input[[paste0("drop",i)]]]))),
multiple=TRUE, selectize=TRUE, selected=inputSelect)) )}
output$drops<- renderUI({
lapply(seq_len(values$number), daStuff)})
By pressing the Calculate button, the uploaded table is subjected to filtering, depending on the selected unique values and shown in the output$table
observeEvent(input$calc, {
values$input<-NULL
for (i in 1:values$number){
if(!is.null(input[[paste0("select",i)]])){
if(is.null(values$input)){
values$input<- filter(values$upload,values$upload[,input[[paste0("drop",i)]]] %in% input[[paste0("select",i)]])}
else{
values$input<- filter(values$input,values$input[,input[[paste0("drop",i)]]] %in% input[[paste0("select",i)]])}
} }
if (is.null(values$input)){values$input<-values$upload}
output$table <- renderTable({values$input})
})
My problem is when I upload a new table (test2.csv), I don't know how to erase the previously stored selections (drop* and select* values) and gives back an error message.
observeEvent(input$new,{
values$upload<-read.csv("test2.csv")
})
}
shinyApp(ui=ui, server = server)
I suppose I should stop somehow the lapply loop and restart it over, so the previously stored values are replaced depending on the new selection, but I am a bit stuck on how I could achieve that.

Answer 1

Just in case you might still be looking for solutions, I wanted to share something that was similar and could potentially be adapted for your needs.
This uses observeEvent for all select inputs. If it detects any changes, it will update all inputs, including the possibilities for select based on drop.
In addition, when a new file is read, the selectInput for drop and select are reset to first value.
Edit: I forgot to keep selected = input[[paste0("drop",i)]] in place for the dropdown (see revised code). It seems to keep the values now when new filters are added - let me know if this is what you had in mind.
library(shiny)
library(shinydashboard)
library(dplyr)
myDataFrame <- read.csv("test.csv")
ui <- shinyUI(
pageWithSidebar(
headerPanel("Testing of dynamic number of selection"),
sidebarPanel(
fileInput("file1", "Choose file to upload", accept = ".csv"),
uiOutput("buttons")
),
mainPanel(
uiOutput("inputs"),
tableOutput("table")
)
)
)
server <- function(input, output, session) {
myInputs <- reactiveValues(rendered = c(1))
myData <- reactive({
inFile <- input$file1
if (is.null(inFile)) {
d <- myDataFrame
} else {
d <- read.csv(inFile$datapath)
}
d
})
observeEvent(lapply(paste0("drop", myInputs$rendered), function(x) input[[x]]), {
for (i in myInputs$rendered) {
updateSelectInput(session,
paste0('select', i),
choices = myData()[input[[paste0('drop', i)]]],
selected = input[[paste0("select",i)]])
}
})
output$buttons <- renderUI({
div(
actionButton(inputId = "add", label = "Add"),
actionButton(inputId = "calc", label = "Calculate")
)
})
observeEvent(input$add, {
myInputs$rendered <- c(myInputs$rendered, max(myInputs$rendered)+1)
})
observeEvent(input$calc, {
showData <- NULL
for (i in 1:length(myInputs$rendered)) {
if(!is.null(input[[paste0("select",i)]])) {
if(is.null(showData)) {
showData <- filter(myData(), myData()[,input[[paste0("drop",i)]]] %in% input[[paste0("select",i)]])
}
else {
showData <- filter(showData, showData[,input[[paste0("drop",i)]]] %in% input[[paste0("select",i)]])
}
}
}
if (is.null(showData)) { showData <- myData() }
output$table <- renderTable({showData})
})
observe({
output$inputs <- renderUI({
rows <- lapply(myInputs$rendered, function(i){
fluidRow(
column(6, selectInput(paste0('drop',i),
label = "",
choices = colnames(myData()),
selected = input[[paste0("drop",i)]])),
column(6, selectInput(paste0('select',i),
label = "",
choices = myData()[1],
multiple = TRUE,
selectize = TRUE))
)
})
do.call(shiny::tagList, rows)
})
})
}
shinyApp(ui, server)