observe not registering reactive value

[vlaf]

Hello,

I am using a reactive value (df_age) in an observer and the expression is never re-evaluated when df_age changes.
Here is the code:

  observe({
    plot_age <- adaptative_dot_plot(
      df_age(),
      df_age()$pat_age
    )

    output$plot_age <- plot_age
    output$plot_age_zoomed <- plot_age
  })

How do I know df_age is reactive changes? I added observe(message(nrow(df_age()))) right before the observer and it prints a message when df_age is changed.

I have also done another experiment. I have added message(nrow(df_age())) to the first line of the observer and magically the observer is now reactive to changes to df_age!

The observer does not seem to register that it should update when df_age updates.

If anyone has an idea to solve this issue...
Thank you!

[pieterjanvc]

Hi,

Welcome to the RStudio community!

Reactive expression are only evaluated when they are needed. It is hard to guess from just this piece of code, but one thing that is a bit weird is you seem to be updating plots (output$plot_age, output$plot_age_zoomed) without using a renderPlot() function.

The observe is not the best reactive wrapper in this case, you would want to either make a reactive variable or put code in the render plot function.

library(shiny)

ui <- fluidPage(
  
  actionButton('myButton', "click"),
  plotOutput("plot1"),
  plotOutput("plot2")
  
)

server <- function(input, output) {
  
  dataPlot1 = reactive({
    input$myButton
    plot(data.frame(x = 1:5, y = runif(5)))
  })
  
  output$plot1 = renderPlot({
    dataPlot1()
  })
  
  output$plot2 = renderPlot({
    input$myButton
    plot(data.frame(x = 1:5, y = runif(5)))
  })
  
}

shinyApp(ui, server)

Please provide a reprex if this is not what you are looking for. Shiny debugging and reprex guide

Hope this helps,
PJ

[vlaf]

Ok thank you.
I had the renderPlotly in the adaptative_dot_plot function and it was not working that way.
Now that renderPlotly is out of the function it works.

thanks!