Question
Hi everyone, could someone explain me how the sdmag parameter is calculated from the following statement? Thanks in advance. [mag,phase,wout,sdmag,sdphase] = bode(sys,w);
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Expert Answer
Kshitij Singh
PhD Expert
Answered Nov 20, 2025
Those are only calculated for identified systems.
If you edit the bode.m here (to simply look through rather than edit the code):
C:\Program Files\MATLAB\R2018b\toolbox\shared\controllib\engine\@DynamicSystem\bode.m % Shadowed DynamicSystem method
you will find that it then refers to magphaseresp_.m and from there to freqresp.m, that among other outputs returns ‘covH’, the covariance of the frequency response of the identified model. That appears to be the source of the standard deviations for the magnitude and phase.
I will let you explore those at your leisure.
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