def get_tax_groups(file):
    """
    Create mapping between taxonomic groups and the relative abundance of that group in each sample
    
    Arguments:
        file (map) -- map representation of relative abundance input file
    
    Returns:
        relAbs (dict) -- maps tax group index (determined by which column it is in the csv file) to list of the group name and relative abundances per sample (e.g.: {1: ['Streptococcus', 0.5, 0.25, 0.25]})
    """
    relAbs = {}
    
    line_counter = 0
    for s in file:
        _ = s.split(",")
        if line_counter == 0:
            for i in range(1,len(_)):
                relAbs[i] = [_[i]]
            line_counter = 1
            continue
    
        for i in range(1,len(_)): # skip first column = sampleID  
            relAbs[i].append(float(_[i]))  

    return relAbs