Download a table created in Shiny - r

Question

I need to give users a set of 60 observations. I have a master table that I want to to subset these 60 observations from. So, (1) I host the master table as a published csv file on google drive. (2) Write a shiny code to subset 60 values in R studio. The user will have to enter a group ID that I use as set.seed and ensure that the user sees the same subset every time he / she attempts to get the 60 observations. And, it also helps me keep track of the observations that the user has.
The code works fine and I am able to show the subset table. But, I am not able to get the download to work. I saw a post that says renderTable create an HTML table that cannot be downloaded and I should create the table outside it. I tried using reactive to do this, but it did not work and kept giving various errors. For example:
"cannot coerce class ‘c("reactiveExpr", "reactive", "function")’ to a data.frame"
Will appreciate any help of this - even if someone can please point out to what I should read and try to make this work.
library(shiny)
db1 <- read.csv("https://docs.google.com/spreadsheets/d/e/2PACX-1vS94xYLix6bDUNNXAgHejdQ-CcWi-G4t25nfxuhRZF57TloC8NwVgnperBB9-U-IuDvMcOnvdc9iavU/pub?gid=0&single=true&output=csv")
# Define UI
ui <- fluidPage(
# Application title
titlePanel("MnM"),
# Sidebar to take input of group ID
sidebarLayout(
sidebarPanel(
numericInput("seed","Group ID:", value = 100, min = 100, max = 999),
downloadButton("downloadData", "Download")
),
# Show the table
mainPanel(
tableOutput("table")
)
)
)
# Define server logic for the table
server <- function(input, output) {
output$table <- renderTable({
set.seed(input$seed)
zz <- sample(1:nrow(db1), size = 60, replace = TRUE)
data.frame(db1[zz,])})
output$downloadData <- downloadHandler(
filename = "test.csv",
content = function(file) {
write.csv(output$table, file, row.names = FALSE)
}
)
}
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

Create your table once, and then use it in your renderTable and downloadHandler. Create it as a reactive, so its available everywhere.
Note that downloadHandler doesn't work in RStudio's preview, view it in a browser instead. There is a button labelled 'Open in Browser' that will do this.
Here is your code with that applied:
library(shiny)
db1 <- read.csv("https://docs.google.com/spreadsheets/d/e/2PACX-1vS94xYLix6bDUNNXAgHejdQ-CcWi-G4t25nfxuhRZF57TloC8NwVgnperBB9-U-IuDvMcOnvdc9iavU/pub?gid=0&single=true&output=csv")
# Define UI
ui <- fluidPage(
# Application title
titlePanel("MnM"),
# Sidebar to take input of group ID
sidebarLayout(
sidebarPanel(
numericInput("seed","Group ID:", value = 100, min = 100, max = 999),
downloadButton("downloadData", "Download")
),
# Show the table
mainPanel(
tableOutput("table")
)
)
)
# Define server logic for the table
server <- function(input, output) {
#Create dataframe
mytable <- reactive({
set.seed(input$seed)
zz <- sample(1:nrow(db1), size = 60, replace = TRUE)
data.frame(db1[zz,])
})
#Display dataframe in table
output$table <- renderTable({
mytable()
})
#Download dataframe
output$downloadData <- downloadHandler(
filename = "test.csv",
content = function(file) {
write.csv(mytable(), file, row.names = FALSE)
}
)
}
# Run the application
shinyApp(ui = ui, server = server)