def line_math(fx=None, fy=None, axes='gca'):
    """
    applies function fx to all xdata and fy to all ydata.
    """

    if axes=='gca': axes = _pylab.gca()

    lines = axes.get_lines()

    for line in lines:
        if isinstance(line, _mpl.lines.Line2D):
            xdata, ydata = line.get_data()
            if not fx==None: xdata = fx(xdata)
            if not fy==None: ydata = fy(ydata)
            line.set_data(xdata,ydata)

    _pylab.draw()
applies function fx to all xdata and fy to all ydata.