Adjust number of digits for small pvalue to be displayed in title of a plot using renderPlot in Shiny in R

user_9476887 0
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In R one can use options(digits=n) to adjust the number of digits in the output value. However, this does not work in Shiny, and sprintf() does not work with very low numbers either since it would only display zeros. So, how could i obtain in Shiny something like

options(digits = 4)

p.val$p.value [1] 3.724e-23

So that i could use it in the title of the plot in renderPlot?

shiny p-value digits plot r
1 Answers

Instead of changing options, we can simply use signif to set our required number of digits. The following mini app can be modified as necessary to work for plot titles.

library(shiny)
ui <- fluidPage(
  fluidRow(
    column(6,
           
           numericInput(
             "hello_options",
             label = "Number",
             value = 3.145677177118
           )),
    
    column(6, 
           numericInput("digits",
                        label = "Digits",
                        value = 4
                        )
           )
  ),
  
  
  textOutput("out_text")

)

server <- function(input, output, server){
    output$out_text <- renderText(
      signif(input$hello_options, digits = input$digits)
    )
}

shinyApp(ui = ui, server = server)

If you want to format to scientific, then change your server to this. Note however that this gives you characters that should be converted back.

server <- function(input, output, server){
    output$out_text <- renderText(
      format(signif(input$hello_options, digits = input$digits),
             scientific = TRUE)
    )
}
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