bode_plot¶

MATLAB equivalent: sidBodePlot

bode_plot ¶

Bode diagram with confidence bands.

bode_plot ¶

bode_plot(result: FreqResult, *, confidence: float = 3.0, frequency_unit: str = 'rad/s', color: str | tuple = None, line_width: float = 1.5, ax: tuple | None = None) -> dict

Bode diagram (magnitude and phase) with shaded confidence bands.

This is the Python port of sidBodePlot.m.

Plots the magnitude (dB) and phase (degrees) of the estimated frequency response. When uncertainty information is available, a shaded region shows the +/- confidence-sigma band.

Parameters:

Name	Type	Description	Default
`result`	`FreqResult`	Result struct returned by :func:`sid.freq_bt`, :func:`sid.freq_etfe`, or :func:`sid.freq_btfdr`. Must contain a non-`None` `response` field (input-output mode).	required
`confidence`	`float`	Number of standard deviations for the shaded confidence band. Set to `0` to hide the bands. Default is `3.0`.	`3.0`
`frequency_unit`	`str`	`'rad/s'` (default) or `'Hz'`.	`'rad/s'`
`color`	`str or tuple`	Line and fill colour. Default is `'#0072BD'` (MATLAB blue).	`None`
`line_width`	`float`	Line width. Default is `1.5`.	`1.5`
`ax`	`tuple of (ax_mag, ax_phase) or None`	Existing matplotlib axes to plot into. If `None`, a new figure with two vertically-stacked subplots is created.	`None`

Returns:

Type	Description
`dict`	Dictionary with the following keys: `'fig'` -- matplotlib Figure handle. `'ax_mag'` -- Axes handle for the magnitude subplot. `'ax_phase'` -- Axes handle for the phase subplot. `'line_mag'` -- Line2D handle for the magnitude trace. `'line_phase'` -- Line2D handle for the phase trace.

Raises:

Type	Description
`SidError`	If `result.response` is `None` (time-series mode). Use :func:`sid.spectrum_plot` instead (code: `'no_response'`).

Examples:

>>> import numpy as np
>>> import sid
>>> N = 1000; u = np.random.randn(N)
>>> y = np.convolve(u, [1, -0.9])[:N] + 0.1 * np.random.randn(N)
>>> result = sid.freq_bt(y, u)
>>> h = sid.bode_plot(result, confidence=3)

Notes

Specification: (Bode plotting -- not yet in SPEC.md)

For MIMO systems only the first SISO channel pair (0, 0) is plotted.