Function _cancelPZ

SLiCAP/SLiCAPmath.py:332–381

Cancels poles and zeros that coincide within the displayed accuracy. :note: The display accuracy (number of digits) is defined by ini.disp. :param poles: List with poles (*float*) of a Laplace rational function. :type poles: list :param zeros: List with zeros (*float*) o

(poles, zeros)

    return rational

def _cancelPZ(poles, zeros):
    """
    Cancels poles and zeros that coincide within the displayed accuracy.

    :note:

    The display accuracy (number of digits) is defined by ini.disp.

    :param poles: List with poles (*float*) of a Laplace rational function.
    :type poles: list

    :param zeros: List with zeros (*float*) of a Laplace rational function.
    :type zeros: list

    :return: Tuple with a list with poles (*float*) and a list with zeros (*float*).
    :rtype: Tuple with two lists,
    """
    newPoles = []
    newZeros = []
    # make a copy of the lists of poles and zeros, this one will be modified
    newPoles = [poles[i] for i in range(len(poles))]
    newZeros = [zeros[i] for i in range(len(zeros))]
    for j in range(len(zeros)):
        for i in range(len(poles)):
            cancel = False
            # Check if zero coincides with pole
            diff = poles[i]-zeros[j]
            if not diff:
                cancel = True
            else:
                try:
                    syms = len(list(diff.atoms(sp.Symbol)))
                except:
                    syms = 0
                if not syms:
                    ssum = poles[i]+zeros[j]
                    erel = abs(0.5*diff/ssum)
                    if erel < 10**(-ini.disp):
                        cancel = True
                    else:
                        cancel = False
                else:
                    cancel = False
            if cancel:
                # if the pole and the zero exist in newPoles and newZeros, respectively
                # then remove the pair
                if poles[i] in newPoles and zeros[j] in newZeros:
                    newPoles.remove(poles[i])
                    newZeros.remove(zeros[j])
    return (newPoles, newZeros)

def _zeroValue(numer, denom, var):
    """