Error: replacement has length zero

[Rose]

I am trying to load a graphic generated after a somewhat lengthy calculation. Most of the time it works but sometimes I get an Error: Replacement length zero. The calculation is to generate a dataframe to conduct a 2d histogram. This never happens when I run the code on its own, only when it's presented in a Shiny app. Here's the code to trigger the function:

     output$clustersShow <- renderPlot({        

       if(input$clusterButton > 0) {

         clust.size <- input$clusterSlider

         numTraces <-30

         list_df <- makeClusters(numTraces)

         df1     <- list_df[[1]]

         drops     <- c("Trace")

         df1.clust <- df1[,!(names(df1) %in% drops)]

         df1C            <- bestCluster(df1.clust, clust.size, df1)

         df1C$clusterCat <- factor(df1C$Cluster)

         plot.cats       <- ggplot(df1C, aes(x=Noise, y = AvgC), colour=clusterCat) + geom_point( aes(color=clusterCat, size=4)) 

         plot.cats

       }

     })

It's makeClusters() that takes a while. I don't see this fitting into the isolate() or reactive() functions, but perhaps I am missing something. How can I get renderPlot to defer presenting the view until makeClusters() and subsequent functions return?

[Joe Cheng]

renderPlot does wait for makeClusters and the rest of the code to finish before returning.

I'd insert a browser() call right before (or maybe after) makeClusters() and walk through the code one line at a time to see where it fails. 

Sent from Outlook

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