How to download datatable after editing in shiny - r

Question

I have about 20 thousand images in a datatable in a shiny application. I want to delete images I dont like and then download the resulting datatable (just with pathnames to the images I want).
I have managed to see a dataframe with each row showing me an image. I can delete rows I dont like. I'd like now to be able to download the dataframe (just with the paths of the files rather than the actual images) into a csv. I don't seem to be able to do this using the downloadHandler. What am I missing?
Here is my code:
server.R
library(shiny)
library(shinydashboard)
library(data.table)
library(DT)
server<-shinyServer(function(input, output) {
vals<-reactiveValues()
vals$Data<-data.table(
df
)
output$MainBody<-renderUI({
fluidPage(
box(width=12,
hr(),
column(12,dataTableOutput("Main_table")),
tags$script(HTML('$(document).on("click", "input", function () {
var checkboxes = document.getElementsByName("row_selected");
var checkboxesChecked = [];
for (var i=0; i<checkboxes.length; i++) {
if (checkboxes[i].checked) {
checkboxesChecked.push(checkboxes[i].value);
}
}
Shiny.onInputChange("checked_rows",checkboxesChecked);
})')),
tags$script("$(document).on('click', '#Main_table button', function () {
Shiny.onInputChange('lastClickId',this.id);
Shiny.onInputChange('lastClick', Math.random())
});")
)
)
})
output$downloadData <- downloadHandler(
filename = function() {
paste(input$Main_table, ".csv", sep = "")
},
content = function(file) {
write.csv(vals$Data, file, row.names = FALSE)
}
)
output$Main_table<-renderDataTable({
DT=vals$Data
datatable(DT,
escape=F)}
)
})
ui.R
ui<-fluidPage(dashboardHeader(disable = T),
dashboardSidebar(disable = T),
downloadLink("downloadData", "Download"),
dashboardBody(uiOutput("MainBody")
)
)
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

The problem is that df is a function from library(stats). Please see ?df. Please, never use df as a variable name - this only causes confusion; take DF instead. You wrapped this function into data.table() and passed it into a reactiveValue (see the print() I added).
This construct is treated as a list() by write.csv() and it doesn't know what do do with a list() causing the following error:
Error in write.table: unimplemented type 'list' in 'EncodeElement'
Accordingly you might want to fix your data.table initialization by e.g. passing NULL instead of df:
library(shiny)
library(shinydashboard)
library(data.table)
library(DT)
server <- shinyServer(function(input, output) {
vals <- reactiveValues(myTabData = data.table(NULL))
vals$Data <- data.table(df)
print(paste("myData:", isolate(vals$Data)))
output$MainBody <- renderUI({
fluidPage(box(
width = 12,
hr(),
column(12, dataTableOutput("Main_table")),
tags$script(
HTML(
'$(document).on("click", "input", function () {
var checkboxes = document.getElementsByName("row_selected");
var checkboxesChecked = [];
for (var i=0; i<checkboxes.length; i++) {
if (checkboxes[i].checked) {
checkboxesChecked.push(checkboxes[i].value);
}
}
Shiny.onInputChange("checked_rows",checkboxesChecked);})'
)
),
tags$script(
"$(document).on('click', '#Main_table button', function () {
Shiny.onInputChange('lastClickId',this.id);
Shiny.onInputChange('lastClick', Math.random())});"
)
))
})
output$downloadData <- downloadHandler(
filename = function() {
"Main_table.csv"
},
content = function(file) {
write.csv(vals$myTabData, file, row.names = FALSE)
# Warning: Error in write.table: unimplemented type 'list' in 'EncodeElement'
# write.csv(vals$Data, file, row.names = FALSE)
}
)
output$Main_table <- renderDataTable({
DT = vals$Data
datatable(DT, escape = FALSE)
})
})
ui <- fluidPage(
dashboardHeader(disable = T),
dashboardSidebar(disable = T),
downloadLink("downloadData", "Download"),
dashboardBody(uiOutput("MainBody"))
)
shinyApp(ui = ui, server = server)
Furthermore you should fix your filename (input$Main_table is not existing)