is_first_order

typhoon.test.signals.is_first_order(signal, time_constant, init_value, final_value, tol, during=None, strictness=1, time_tol=0, report_plot=None)

Checks if signal represents first order response.

Verifies that signal follows exponential equation defined with formula:

x(t) = x(inf) + (x(0) - x(inf)) * exp(-t / tau),

where t represents the time axis of the signal.

Parameters:
  • signal (pandas.Series) – Signal to be tested for.

  • time_constant (float) – Time constant of the signal; represents tau in formula (1).

  • init_value (float) – Initial value of the signal; represents x(0) in formula (1)

  • final_value (float) – Stationary state value of the signal; represents x(inf) in formula (1).

  • tol (float) – Tolerance around which the signal can stay with respect to reference ramp when determining if result is True or False.

  • during (2-element tuple of numbers or Timedelta) – Time period (as a range) to be considered for analysis.

  • strictness (float) – Number between 0.0 and 1.0 that determines percentage of time signal should be inside the defined range for test to pass.

  • time_tol (float or timedelta) – Time tolerance - argument which allows that signal is leading or lagging up to specified time in seconds, compared to created reference.

  • report_plot (dict) –

    Dictionary which overrides default allure report plot attachment behaviour. It also overrides behaviour specified for whole test run with command line arguments --analysis-plot-type and --analysis-plot-on-fail-only. Dictionary has two keys to be specified:

    1. type: specifies which kind of allure plot should be used. Valid values:

      • static - only matplotlib plot attached as .png picture is attached

      • interactive - only interactive html plot created with bokeh library is attached. Advantage of this plot it has options to zoom in/zoom out. Disadvantage is that it consumes significantly more memory.

      • none - none of the plots will be attached

      • all - all plots will be added. Currently supported ones are matplotlib plot(static) and bokeh plot(interactive)

    2. when: specifies when to add plots that are specified with previous key to report. Available options:

      • always - always adds specified plots

      • on-fail - adds plots only if comparison of reference and measured signal fails. This is good way to decrease size of allure plots.

    Note

    If report_plot argument is not provided, and command line arguments --analysis-plot-type and analysis-plot-on-fail-only are not specified, default behaviour is static plot, attached always. If command line arguments are specified, they define new default behaviour for whole test run.

Returns:

result – Result of the analysis.

Return type:

AnalysisResult

Examples

>>> import typhoon.test.signals as signals
>>> tau = 0.1
>>> init = 0
>>> fin = 10
>>> exp_sig = signals.pandas_first_order(tau, init, fin) # first order response signal
>>> assert signals.is_first_order(exp_sig, tau, init, fin, tol=0.01*fin)