subtle ggplot2 techniques

  1. Histograms (geom_histogram) display the count with bars;
    frequency polygons (geom_freqpoly), display the counts with lines.
  2. how to remove extra base line in ggplot2-density plots? (https://groups.google.com/forum/#!topic/ggplot2/I3fXMH8foEs) ggplot(a,aes(x=V1))+geom_density() = ggplot(a,aes(x=V1))+geom_line(stat=”density”)