plottype
    If plottype="persample", each sample is plotted in a separate plot displaying abundance of byotype in genome, percentage of biotype detected by sample and abundance of biotype in sample.
    If plottype="comparison", two samples can be compared in the same plot. Two plots are generated, one for the percentage of biotype detected by each of the compared samples, and the other 
    for the abundance of the biotypes within the compared samples. 
  
toplot
    If plottype="comparison" and a biotype is specified in this argument (by default toplot="protein_coding"), a proportion test is performed to test if the abundance of that biotype
    is significantly different for the two samples being compared.