def default_marker_size(fmt):
    """ Find a default matplotlib marker size such that different marker types
    look roughly the same size.
    """
    temp = fmt.replace('.-', '')
    if '.' in temp:
        ms = 10
    elif 'D' in temp:
        ms = 7
    elif set(temp).intersection('<>^vd'):
        ms = 9
    else:
        ms = 8
    return ms