How to chage the background color of a plot in shiny?

Question

I'm wondering if i can change the background-color of the plot or at least make it transparent allowing to inherit its parent background , I have tried that :

ui:

plotOutput("scatterChart",
                       width = "80%",
                       height = "294px")

server:

  output$scatterChart <- renderPlot({
    par(bg = "yellow")
    plot(rules(), col  = rainbow(25), cex  = input$cex)
  })

as shown here : https://stat.ethz.ch/pipermail/r-help/2003-May/033971.html

but nothing changed .

I tried that with css :

#scatterChart{
  background-color:red}

i didn't get the expected result .

or :

.shiny-plot-output{
  background-color:red
}

that change the entire div background and i even can't see the plot itself(i was exepecting that ).

Here is a picture : demo

EDITED :

Based on the example that thothal gives me , i discover that the problem was on the data passed to the plot function (it just some association rules obtained using Apriori algorithm) :

rules <- reactive({
    head(read.csv(input$file$datapath), input$visualization)
    transactions = read.transactions(
      file = file(input$file$datapath),
      format = "basket",
      sep = ","
    )
    minValue <- min(length(transactions),input$visualization)
    rules <-
      apriori(transactions[0:minValue],
              parameter = list(
                support = input$min_supp,
                confidence = input$min_conf
              ))
    return(rules)
  })

Any suggestions or advice would be appreciated. Thanks.

Answer 1

Actually you can simply change the background color of you plot like this

library(shiny)
ui <- fluidPage(plotOutput("p"), actionButton("go", "Go"))

server <- function(input, output) {

   output$p <- renderPlot({
      input$go
      par(bg = "navyblue")
      x <- rnorm(100)
      plot(x, 5 * x + rnorm(100, sd = .3), col = "white")
   })
}

shinyApp(ui, server)

This produces the following plot on my machine:

As you tried the very same, I was wondering what happens if you try to create the plot outside shiny does it show (with the respective par call) a colorful background?

Maybe some other settings in you app may override this behaviour. Can you try to run my code and see what happens?

---

If you use another plotting library (ggplot for instance) you have to adapt and use

theme(plot.background = element_rect(...), # plotting canvas
      panel.background = element_rect(...)) # panel

---

Update

It turns out that the culprit is arulesViz:::plot.rules, which is grid based and ignores settings set via par. To get a colored background we have to add a filled rect to the right viewport.

I forked the original repo and provided a quick fix of that:

devtools::install_github("thothal/arulesViz@add_bg_option_scatterplot")
data(Groceries)
rules <- apriori(Groceries, parameter=list(support=0.001, confidence=0.8))

## with my quick fiy you can now specify a 'bg'  option to 'control'

plot(rules, control = list(bg = "steelblue")

Answer 2

We can use bg argument inside renderPlot:

output$plot1 <- renderPlot({

  # your plot

}, bg = "red")