rJava, rCharts and R code to display GC data

These are the steps I follow to display GC activity data using a nvd3 discrete bar chart.

Call Java class using rJava

  gctypes <- .jcall(realtimegcdataobserver ,"Ljava/util/List;","getGCTypes")

Create an empty data frame to hold the data

I get the type of the GC algorithm, GC count and time from JMX. I have yet to explore the last two values.

gcdata <- function(){
  df <- data.frame(
                 GCType=character(), 
                 Count=character(),
                 Time=character(), 
                 stringsAsFactors=FALSE)
  print(df)
  return(df)
}

Iterate over the list of beans

Call appropriate methods and fill up the empty data frame.
I massage the data using the last two lines but don’t know any elegant way to accomplish this.

  emptygcdata <- gcdata()
  gctypedetails <- sapply( gctypes, function(item) rbind(emptygcdata, as.data.frame(c(GCType=item$getName(),Count=item$getL(),Time=item$getM()))))

  gctypedetails <- data.frame(gctypedetails)
  gctypedetails <- data.frame(matrix(unlist(gctypedetails)))

matrix.unlist.gctypedetails..
1 PS Scavenge
2 16
3 22
4 PS MarkSweep
5 0
6 0

emptygcdata <- gcdata()
  before <- 0
  after <- 2
  repeat
  {
    if (after >= nrow(gctypedetails))
     break;
    emptygcdata <- rbind(emptygcdata, data.frame(GCType =gctypedetails[before + 1,1], Count =gctypedetails[before + 2,1], Time=gctypedetails[before + 3,1]))
    before <- after + 1;
    after <- after + 2;
   }

 GCType          Count  Time
1  PS Scavenge      16  22
2  PS MarkSweep     0  0

nvd3 using rCharts

  p2 = nPlot(x = "Time", y = "Count", data = emptygcdata, type = "discreteBarChart")
  p2$chart(
    color = "#! function(d){
      var ourColorScale = d3.scale.ordinal().domain(['PS MarkSweep','PS Scavenge']).range(['green','purple']);
      return ourColorScale(d.GCType);
    }!#")