Interactive Shiny Table Download and Page Length Issues - shiny

Question

The code below is adapted from https://gist.github.com/wch/4211337 and perfectly illustrates my challenges. I have two main issues:
I cannot get the interactive tables to download; and
I can't figure out how to make the table print with a page length, for example that shows 25 rows and lets you toggle to the next page.
Here is the code:
server.r
data_sets <- c("mtcars", "morley", "rock")
shinyServer(function(input, output) {
# Drop-down selection box for which data set
output$choose_dataset <- renderUI({
selectInput("dataset", "Data set", as.list(data_sets))
})
# Check boxes
output$choose_columns <- renderUI({
# If missing input, return to avoid error later in function
if(is.null(input$dataset))
return()
# Get the data set with the appropriate name
dat <- get(input$dataset)
colnames <- names(dat)
# Create the checkboxes and select them all by default
checkboxGroupInput("columns", "Choose columns",
choices = colnames,
selected = colnames)
})
# Output the data
output$data_table <- renderTable({
# If missing input, return to avoid error later in function
if(is.null(input$dataset))
return()
# Get the data set
dat <- get(input$dataset)
# Make sure columns are correct for data set (when data set changes, the
# columns will initially be for the previous data set)
if (is.null(input$columns) || !(input$columns %in% names(dat)))
return()
# Keep the selected columns
dat <- dat[, input$columns, drop = FALSE]
# Return
dat
})
output$downloadData <- downloadHandler(
filename = function() {
('test.csv')
},
content = function(con) {
write.table(dat, row.names = FALSE, col.names=T, sep=",",con)
},
contentType="csv"
)
})
ui.r
shinyUI(pageWithSidebar(
headerPanel(""),
sidebarPanel(
uiOutput("choose_dataset"),
uiOutput("choose_columns"),
downloadButton("downloadData", style = "color: white;background-color: #303030")
),
mainPanel(
tableOutput("data_table")
)
))
I am getting an error code in the downloadHandler that says it doesn't recognize dat. I have tried wrapping the elements in reactive({}), but that didn't work either.
I have tried several things to get the table to show with a page length, but nothing I am doing is working, so I don't have any code for that presented here.
Thanks for any help!

Answer 1

Just do the data wrangling outside. Try this
server <- shinyServer(function(input, output) {
# Drop-down selection box for which data set
output$choose_dataset <- renderUI({
selectInput("dataset", "Data set", as.list(data_sets))
})
# Check boxes
output$choose_columns <- renderUI({
# If missing input, return to avoid error later in function
if(is.null(input$dataset))
return()
# Get the data set with the appropriate name
dat <- get(input$dataset)
colnames <- names(dat)
# Create the checkboxes and select them all by default
checkboxGroupInput("columns", "Choose columns",
choices = colnames,
selected = colnames)
})
dat <- reactive({
# If missing input, return to avoid error later in function
if(is.null(input$dataset))
return()
# Get the data set
dat <- get(input$dataset)
# Make sure columns are correct for data set (when data set changes, the
# columns will initially be for the previous data set)
if (is.null(input$columns) || !(input$columns %in% names(dat)))
return()
# Keep the selected columns
dat <- dat[, input$columns, drop = FALSE]
# Return
dat
})
# Output the data
output$data_table <- renderTable({
dat()
})
output$downloadData <- downloadHandler(
filename = function() {
('test.csv')
},
content = function(con) {
write.table(dat(), row.names = FALSE, col.names=T, sep=",",con)
},
contentType="csv"
)
})