diff --git a/utils/hyperloglog/hll-gnuplot-graph.rb b/utils/hyperloglog/hll-gnuplot-graph.rb
index 1cccbf4be82aba24ccda26257bf64fa3e0bc3c44..468eb99cf215e33bf358695d353fcd0cdca00f84 100644
--- a/utils/hyperloglog/hll-gnuplot-graph.rb
+++ b/utils/hyperloglog/hll-gnuplot-graph.rb
@@ -47,6 +47,7 @@ def filter_samples(numsets,filter)
         dataset[i] = run_experiment(r,i,100000,1)
     }
     dataset[0].each_with_index{|ele,index|
+        ele[1] = ele[1].abs if filter == :max
         card,err=ele
         if filter == :max
             (1...numsets).each{|i|