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Refresh all the drawing axes of the iiplot interface.




iiplot used as a command with no arguments is the user entry point to refresh all the drawing axes. Section 2.1 gives an introduction to the use of iiplot and the companion function iicom (compatibility issues with SDT 5 are discussed in section 2.1.6).

ci=iiplot returns a SDT handle to the current iiplot figure (2nd optionnal output argument is XF, a pointer to the curve stack, see  section 2.1.2). You can create more than one iiplot figure with ci=iiplot(FigHandle).

Each iiplot axis can display some or all data sets in their stack. The selection of what is displayed is obtained using the iicom IIx commands or the Variables menu.

You can create a new iiplot axis using a curve data structure Curve (generated by fe_curve for example), simply calling iiplot(Curve).

Plot types supported by iiplot are described below. The plot type can be selected using the PlotType menu of the toolbar or through iicom Show commands.

Selected channels (columns of the data sets) are shown for all plots. The iicom commands +, -, ch and the associated keys and toolbar buttons can be used to change selected channels.

Pole lines for the indication of pole frequencies are available for many plots. The iicom PoleLine commands and the IIplot:PoleLine menu can be used to change how these lines appear. ci.Stack{'IdMain'} pole lines are shown in white/black.
ci.Stack{'IdAlt'} pole lines in red.


Basic plots are amplitude of response (initialized by iicom('show abs')), phase of response wrapped (show pha) or unwrapped (show phu), real part of the response (show rea), imaginary part (show ima), real and imaginary parts (show r&i), or Nyquist plot(real versus imaginary part, show nyq).

Local Nyquist

Local Nyquist plots (initialized by show lny) show a comparison of IIxf (measured FRFs) and IIxe (identified model) in a reduced frequency band


near the currently selected pole (the current pole is selected by clicking on a pole line in another plot axis). Local Nyquist plots allow a local evaluation of the quality of the fit. The error and quality plots give a summary of the same information for all the frequency response functions and all poles.


Multivariate Mode Indicator Function (initialized by show mmi), forces associated to the MMIF (initialized by show fmi), Alternate Mode Indicator Function (show ami), and Channel Sum (show sum) are four ways to combine all the FRFs or a set to get an indication of where its poles are located.

These indicators are discussed in the ii_mmif Reference section. They are automatically computed by iiplot based on data in the 'Test' set.

Pole, Freq/damp,Residues

Pole locations in the complex plane (initialized by show pol).

Poles shown as damping vs. frequency are initialized by show fre.

Position of residues in the complex plane are initialized by show cre. This plot can be used to visualize the phase scatter of identified residues.

Value of real residue for each measured channel are initialized by show rre.

Error, Quality

Local Nyquist error (initialized by show err). For the current pole, error plots select frequency points in the range [ωj(1−ζj) ωj(1+ζj)]. For each channel (FRF column), the normalized error (RMS response of ci.Stack{'Test'}.xf - ci.Stack{'IdMain'}.xf divided by RMS response of ci.Stack{'Test'}) is shown as a dashed line with + markers and a normalized response level (RMS response of ci.Stack{'Test'}) as a dashed line with x markers.

Normalized errors should be below 0.1 unless the response is small.

Mode quality plot (initialized by show qua), gives a mean of the local Nyquist plot. The dashed lines with + and x markers give a standard and amplitude weighted mean of the normalized error. The dotted line gives an indication of the mean response level (to see if a mode is well excited in the FRFs). Normalized errors should be below 0.1 unless the response is small.

See also

iicom, iiplot, setlines, xfopt

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