I'm trying to write a little app that will allow the user to make a scatterplot, select a subset of points on the plot, then output a table in .csv format with just those selected points. I figured out how to get the page up and running and how to select points using brushedPoints. The table with selected points appears but when I press the Download button, the error "Reading objects from shinyoutput object not allowed." appears. Am I unable to download the table that I can visually see on the screen as a .csv? If so, is there a workaround?
I've recreated the problem using the iris dataset below. Any help figuring out why I cannot download the table of displayed rows would be greatly appreciated.
data(iris)
ui <- basicPage(
plotOutput("plot1", brush = "plot_brush"),
verbatimTextOutput("info"),mainPanel(downloadButton('downloadData', 'Download'))
)
server <- function(input, output) {
output$plot1 <- renderPlot({
ggplot(iris,aes(x=Sepal.Width,y=Sepal.Length)) +
geom_point(aes(color=factor(Species))) +
theme_bw()
})
output$info <- renderPrint({
brushedPoints(iris, input$plot_brush, xvar = "Sepal.Width", yvar = "Sepal.Length")
})
output$downloadData <- downloadHandler(
filename = function() {
paste('SelectedRows', '.csv', sep='') },
content = function(file) {
write.csv(output$info, file)
}
)
}
shinyApp(ui, server)
Best Answer
The issue is that the output object is generating all of the web display stuff as well. Instead, you need to pull the data separately for the download. You could do it with a second call to
brushedPoints
in the download code. Better, however, is to use areactive()
function to do it just once, then call that everywhere that you need it. Here is how I would modify your code to make that work:(Note, with
ggplot2
, you do not need to explicitly setxvar
andyvar
inbrushedPoints
. So, I removed it here to increase the flexibility of the code.)I am not aware of any "lasso" style free drawing ability in
shiny
(though, give it a week -- they are constantly adding fun tools). However, you can mimic the behavior by allowing user to select multiple regions and/or to click on individual points. The server logic gets a lot messier, as you need to store the results in areactiveValues
object to be able to use it repeatedly. I have done something similar to allow me to select points on one plot and highlight/remove them on other plots. That is more complicated than what you need here, but the below should work. You may want to add other buttons/logic (e.g., to "reset" the selections), but I believe that this should work. I did add a display of the selection to the plot to allow you to keep track of what has been selected.