compareOptions
Option set for compare
Description
Use a compareOptions
object to specify options for comparing
identified model output with measured output through the compare
function. You can specify options such as the handling of initial
conditions or the output weight to be used in estimation.
Creation
Properties
Samples
— Data for which compare
calculates fit values
vector | cell array
compare
Specify Samples
as a vector containing the data sample indices.
For multiexperiment data, use a cell array of Ne vectors, where
Ne is the number of experiments.
InitialCondition
— Handling of initial conditions
'e'
(default) | 'z'
Handling of initial conditions.
Specify InitialCondition
as one of the following:
'z'
— Zero initial conditions.'e'
— Estimate initial conditions such that the prediction error for observed output is minimized.For nonlinear grey-box models, only those initial states
i
that are designated as free in the model (sys.InitialStates(i).Fixed = false
) are estimated. To estimate all the states of the model, first specify all theNx
states of theidnlgrey
modelsys
as free.for i = 1:Nx sys.InitialStates(i).Fixed = false; end
Similarly, to fix all the initial states to values specified in
sys.InitialStates
, first specify all the states as fixed in thesys.InitialStates
property of the nonlinear grey-box model.'d'
— Similar to'e'
, but absorbs nonzero delays into the model coefficients. The delays are first converted to explicit model states, and the initial values of those states are also estimated and returned.Use this option for linear models only.
Vector or Matrix — Initial guess for state values, specified as a numerical column vector of length equal to the number of states. For multiexperiment data, specify a matrix with Ne columns, where Ne is the number of experiments. Otherwise, use a column vector to specify the same initial conditions for all experiments. Use this option for state-space (
idss
andidgrey
) and nonlinear models (idnlarx
,idnlhw
, andidnlgrey
) only.initialCondition
object —initialCondition
object that represents a model of the free response of the system to initial conditions. For multiexperiment data, specify a 1-by-Ne array of objects, where Ne is the number of experiments.Use this option for individual linear models only. If you are analyzing more than one model and want to specify an
initialCondition
object for each model, you must specify the object and usecompare
for each model separately.Structure with the following fields, which contain the historical input and output values for a time interval immediately before the start time of the data used by
compare
:Field Description Input
Input history, specified as a matrix with Nu columns, where Nu is the number of input channels. For time series models, use []
. The number of rows must be greater than or equal to the model order.Output
Output history, specified as a matrix with Ny columns, where Ny is the number of output channels. The number of rows must be greater than or equal to the model order. For multiexperiment data, configure the initial conditions separately for each experiment by specifying
InitialCondition
as a structure array with Ne elements. To specify the same initial conditions for all experiments, use a single structure.The software uses
data2state
to map the historical data to states. If your model is notidss
,idgrey
,idnlgrey
, oridnlarx
, the software first converts the model to its state-space representation and then maps the data to states. If conversion of your model toidss
is not possible, the estimated states are returned empty.x0obj
— Specification object created usingidpar
. Use this object for discrete-time state-space (idss
andidgrey
) and nonlinear grey-box (idnlgrey
) models only. Usex0obj
to impose constraints on the initial states by fixing their value or specifying minimum or maximum bounds.
InputInterSample
— Input-channel intersample behavior
'auto'
| 'zoh'
| 'foh'
| 'bl'
Input-channel intersample behavior for transformations between discrete time and
continuous time, specified as 'auto'
,
'zoh'
,'foh'
, or 'bl'
.
The definitions of the three behavior values are as follows:
'zoh'
— Zero-order hold maintains a piecewise-constant input signal between samples.'foh'
— First-order hold maintains a piecewise-linear input signal between samples.'bl'
— Band-limited behavior specifies that the continuous-time input signal has zero power above the Nyquist frequency.
iddata
objects have a similar property,
data.InterSample
, that contains the same behavior value options.
When the InputInterSample
value is 'auto'
and
the estimation data is in an iddata
object data
, the
software uses the data.InterSample
value. When the estimation data
is instead contained in a timetable or a matrix pair, with the 'auto'
option, the software uses 'zoh'
.
The software applies the same option value to all channels and all experiments.
InputOffset
— Removes offset from time domain input data for model response computation
[]
(default) | vector | matrix
Specify as a column vector of length Nu, where Nu is the number of inputs.
Use []
to indicate no offset.
For multiexperiment data, specify InputOffset
as a
Nu-by-Ne matrix. Nu is the
number of inputs and Ne is the number of experiments.
Each entry specified by InputOffset
is subtracted from the
corresponding input data.
OutputOffset
— Removes offset from time-domain output data for model response prediction
[]
(default) | vector | matrix
Specify as a column vector of length Ny, where Ny is the number of outputs.
Use []
to indicate no offset.
For multiexperiment data, specify OutputOffset
as a
Ny-by-Ne matrix. Ny is the
number of outputs and Ne is the number of experiments.
Each entry specified by OutputOffset
is subtracted from the
corresponding output data before computing the model response. After computing the model
response, the software adds the offset to the response to give the final model
response.
OutputWeight
— Weight of output for initial condition estimation
[]
(default) | 'noise'
| matrix of doubles
OutputWeight
requires one of the following values:
[]
— No weighting is used. This option is the same as usingeye(Ny)
for the output weight. Ny is the number of outputs.'noise'
— Inverse of the noise variance stored with the model.Matrix of doubles — A positive semi-definite matrix of dimension Ny-by-Ny. Ny is the number of outputs.
Examples
Create Default Options Set for Model Comparison
Specify Options for Model Comparison
Create an options set for compare
using zero initial conditions. Set the input offset to 5.
opt = compareOptions('InitialCondition','z','InputOffset',5);
Alternatively, use dot notation to set the values of opt
.
opt = compareOptions;
opt.InitialCondition = 'z';
opt.InputOffset = 5;
Version History
Introduced in R2012aR2022b: InputInterSample
option allows intersample behavior specification for continuous models estimated from timetables or matrices.
iddata
objects contain an InterSample
property that
describes the behavior of the signal between sample points. The
InputInterSample
option implements a version of that property in
compareOptions
so that intersample behavior can be specified also when
estimation data is stored in timetables or matrices.
See Also
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