def get_tag_count_data(infilename, chromosome='chr01'):
    """
    Reads in tag count of a particular chromosome.
    Input format is the same as that of GeneTrack/LionDB3
    """
    k_idx = []
    k_fwd = []
    k_rev = []
    for i in  open(infilename):
        isplit = i.split()
        if isplit[0]==chromosome:
            k_idx.append( int(isplit[1]))
            k_fwd.append( int(isplit[2]))
            k_rev.append( int(isplit[3]))
    return k_idx, k_fwd, k_rev