def peakdelta(v, delta, x=None):
    maxtab = []
    mintab = [] 
    if x is None:
        x = arange(len(v))
    v = asarray(v)
    if len(v) != len(x):
        sys.exit('Input vectors v and x must have same length')
    if not isscalar(delta):
        sys.exit('Input argument delta must be a scalar')
    if delta <= 0:
        sys.exit('Input argument delta must be positive')
    mn, mx = Inf, -Inf
    mnpos, mxpos = NaN, NaN
    lookformax = True
    for i in arange(len(v)):
        this = v[i]
        if this > mx:
            mx = this
            mxpos = x[i]
        if this < mn:
            mn = this
            mnpos = x[i]
        if lookformax:
            if this < mx - delta:
                maxtab.append((mxpos, mx))
                mn = this
                mnpos = x[i]
                lookformax = False
        else:
            if this > mn + delta:
                mintab.append((mnpos, mn))
                mx = this
                mxpos = x[i]
                lookformax = True
    return array(maxtab), array(mintab)