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scipy.signal.

# dstep

scipy.signal.dstep(system, x0=None, t=None, n=None)

  Step response of discrete-time system.

  Parameters:
    system dlti | tuple

      An instance of the LTI class `dlti` or a tuple describing the system. The number of elements in the tuple determine the interpretation. I.e.:

      - `system`: Instance of LTI class `dlti`. Note that derived instances, such as instances of `TransferFunction`, `ZerosPolesGain`, or `StateSpace`, are allowed as well.

      - `(num, den, dt)`: Rational polynomial as described in `TransferFunction`. The coefficients of the polynomials should be specified in descending exponent order, e.g., z² + 3z + 5 would be represented as `[1, 3, 5]`.

      - `(zeros, poles, gain, dt)`: Zeros, poles, gain form as described in `ZerosPolesGain`.

      - `(A, B, C, D, dt)`: State-space form as described in `StateSpace`.

    x0 array_like, optional

      Initial state-vector. Defaults to zero.

    t array_like, optional

      Time points. Computed if not given.

    n int, optional

      The number of time points to compute (if t is not given).

  Returns:
    tout ndarray

      Output time points, as a 1-D array.

    yout tuple of ndarray

      Step response of system. Each element of the tuple represents the output of the system based on a step response to each input.

  See also

  `step`, `dimpulse`, `dlsim`, `cont2discrete`

  Examples

  The following example illustrates how to create a digital Butterworth filer and plot its step response:

      >>> import numpy as np
      >>> from scipy import signal
      >>> import matplotlib.pyplot as plt
      ...
      >>> dt = 1  # sampling interval is one => time unit is sample number
      >>> bb, aa = signal.butter(3, 0.25, fs=1/dt)
      >>> t, y = signal.dstep((bb, aa, dt), n=25)
      ...
      >>> fig0, ax0 = plt.subplots()
      >>> ax0.step(t, np.squeeze(y), '.-', where='post')
      >>> ax0.set_title(r"Step Response of a $3^\text{rd}$ Order Butterworth Filter")
      >>> ax0.set(xlabel='Sample number', ylabel='Amplitude', ylim=(0, 1.1*np.max(y)))
      >>> ax0.grid()
      >>> plt.show()