scipy.signal.dlti

class scipy.signal.dlti(*system, **kwargs)

Discrete-time linear time invariant system base class.

Parameters:

*system: arguments

The dlti class can be instantiated with either 2, 3 or 4 arguments. The following gives the number of arguments and the corresponding discrete-time subclass that is created:

• 2: TransferFunction: (numerator, denominator)
• 3: ZerosPolesGain: (zeros, poles, gain)
• 4: StateSpace: (A, B, C, D)

Each argument can be an array or a sequence.

dt: float, optional

Sampling time [s] of the discrete-time systems. Defaults to True (unspecified sampling time). Must be specified as a keyword argument, for example, dt=0.1.

See also

ZerosPolesGain, StateSpace, TransferFunction, lti

Notes

dlti instances do not exist directly. Instead, dlti creates an instance of one of its subclasses: StateSpace, TransferFunction or ZerosPolesGain.

Changing the value of properties that are not directly part of the current system representation (such as the zeros of a StateSpace system) is very inefficient and may lead to numerical inaccuracies. It is better to convert to the specific system representation first. For example, call sys = sys.to_zpk() before accessing/changing the zeros, poles or gain.

If (numerator, denominator) is passed in for *system, coefficients for both the numerator and denominator should be specified in descending exponent order (e.g., z^2 + 3z + 5 would be represented as [1, 3, 5]).

New in version 0.18.0.

Examples

>>> from scipy import signal

>>> signal.dlti(1, 2, 3, 4)
StateSpaceDiscrete(
array([[1]]),
array([[2]]),
array([[3]]),
array([[4]]),
dt: True
)

>>> signal.dlti(1, 2, 3, 4, dt=0.1)
StateSpaceDiscrete(
array([[1]]),
array([[2]]),
array([[3]]),
array([[4]]),
dt: 0.1
)

>>> signal.dlti([1, 2], [3, 4], 5, dt=0.1)
ZerosPolesGainDiscrete(
array([1, 2]),
array([3, 4]),
5,
dt: 0.1
)

>>> signal.dlti([3, 4], [1, 2], dt=0.1)
TransferFunctionDiscrete(
array([ 3.,  4.]),
array([ 1.,  2.]),
dt: 0.1
)

Attributes

A	State matrix of the StateSpace system.
B	Input matrix of the StateSpace system.
C	Output matrix of the StateSpace system.
D	Feedthrough matrix of the StateSpace system.
den	Denominator of the TransferFunction system.
dt	Return the sampling time of the system.
gain	Gain of the ZerosPolesGain system.
num	Numerator of the TransferFunction system.
poles	Poles of the system.
zeros	Zeros of the system.

Methods

bode([w, n])	Calculate Bode magnitude and phase data of a discrete-time system.
freqresp([w, n, whole])	Calculate the frequency response of a discrete-time system.
impulse([x0, t, n])	Return the impulse response of the discrete-time dlti system.
output(u, t[, x0])	Return the response of the discrete-time system to input u.
step([x0, t, n])	Return the step response of the discrete-time dlti system.