getCumulativePosition

def getCumPos(data):
    """
    getCumulativePosition
    """
    pos = getPosNew(data)
    chrom= data.geno['col_header']['chrom'][:]
    n_chroms = int(chrom.max())
    x = 0
    for chrom_i in range(1,n_chroms+1):
        I = chrom==chrom_i
        pos[I]+=x
        x=pos[I].max()
    return pos