Downloading Reactive Dataframe/datatable issue - r

Question

I'm new to R but I was given the task to create a working download button that would download the data within the queried table, to a .csv file. Currently, I'm having trouble understanding what I should pass on to my write.csv() function. I know I have to make the queried table reactive but I'm also unsure how to do that. The error I'm getting with my current code is "
cannot coerce class ‘c("datatables", "htmlwidget")’ to a data.frame"
I've tried passing my df() function as an argument but it doesn't work.
#ui
column(3,
conditionalPanel("input.table.period != '1980'",
# only prompt for rcp if a future period (not historical)
# input: select rcp
selectInput("table.rcp", "Emissions Scenario:",
c("Medium" = "45",
"High" = "85")),
downloadButton('downloadData', 'Download')
)
#server
server <- function(input, output) {
currentdf <- reactive({
# build query based on user-selections
if (input$table.stype == "ann") {
col.name <- columns.annual[grep(input$table.var, columns.annual)]
if (input$table.period == "1980") {
query <- paste0("SELECT ", col.name, ", subbasin, gcm_id FROM hydro_ann WHERE (period = ", input$table.period,
")")
} else {
query <- paste0("SELECT ", col.name, ", subbasin, gcm_id FROM hydro_ann WHERE (period = ", input$table.period,
") AND (rcp = ", input$table.rcp, ")")
}
} else {
col.name <- columns.month[grep(input$table.var, columns.month)]
if (input$table.period == "1980") {
query <- paste0("SELECT ", col.name, ", subbasin, gcm_id, calendar_month FROM hydro_month WHERE (period = ", input$table.period,
")")
} else {
query <- paste0("SELECT ", col.name, ", subbasin, gcm_id, calendar_month FROM hydro_month WHERE (period = ", input$table.period,
") AND (rcp = ", input$table.rcp, ")")
}
}
df <- dbGetQuery(db, query)
DT::df
})
output$querytable <- renderTable({ DT::datatable(currentdf()) })
output$downloadData <- downloadHandler(
filename = function() {
paste("QueriedData", "csv", sep = ".")
},
content = function(file) {
write.csv(as.data.frame(currentdf()),file)
}

Answer 1

I have tried a solution width Iris dataset which can give you option to select datatype you want to save before downloading data as per option you selected...
library(shiny)
library(shinydashboard)
library(DT)
library(datasets)
library(xlsx)
ui <- dashboardPage(
dashboardHeader(title = "Basic dashboard"),
dashboardSidebar(),
dashboardBody(
# Boxes need to be put in a row (or column)
fluidRow(
box(
DTOutput("dtable")
)
)
)
)
server <- function(input, output) {
myModal <- function() {
div(id = "Download_DATA",
modalDialog(downloadButton("download1","Download iris as CSV"),
br(),
br(),
downloadButton("download2","Download iris as XLSX"),
easyClose = TRUE, title = "Download Table")
)
}
output$dtable <- renderDT(
datatable(iris,
extensions = 'Buttons',
options = list(
dom = 'Bfrtip',
buttons = list(
list(
extend = "collection",
text = 'Download',
action = DT::JS("function ( e, dt, node, config ) {
Shiny.setInputValue('Download_DATA', true, {priority: 'event'});
}")
)
)
)
)
)
observeEvent(input$Download_DATA, {
showModal(myModal())
})
output$download1 <- downloadHandler(
filename = function() {
paste("data-", Sys.Date(), ".csv", sep="")
},
content = function(file) {
write.csv(iris, file)
}
)
output$download2 <- downloadHandler(
filename = function() {
paste("data-", Sys.Date(), ".xlsx", sep="")
},
content = function(file) {
write.xlsx(iris, file)
}
)
}
shinyApp(ui, server)
Please let me know....