Specify optional comma-separated pairs of `Name,Value`

arguments.
`Name`

is the argument
name and `Value`

is the corresponding
value. `Name`

must appear
inside single quotes (`' '`

).
You can specify several name and value pair
arguments in any order as `Name1,Value1,...,NameN,ValueN`

.

Specify handling of initial states during estimation, specified
as one of the following strings:

Weighting scheme used for singular-value decomposition by the
N4SID algorithm.

`'N4Weight'`

requires one of the following
values:

`'MOESP'`

— Uses the MOESP
algorithm by Verhaegen [2].

`'CVA'`

— Uses the Canonical
Variable Algorithm by Larimore [1].

Estimation using frequency-domain data always uses `'CVA'`

.

`'SSARX'`

— A subspace identification
method that uses an ARX estimation based algorithm to compute the
weighting.

Specifying this option allows unbiased estimates when using
data that is collected in closed-loop operation. For more information
about the algorithm, see [4].

`'auto'`

— The estimating
function chooses between the `MOESP`

, `CVA`

and `SSARX`

algorithms.

Forward- and backward-prediction horizons used by the N4SID
algorithm.

`'N4Horizon'`

requires one of the following
values:

A row vector with three elements — ` [r sy su]`

,
where `r`

is the maximum forward prediction horizon,
using up to `r`

step-ahead predictors. `sy`

is
the number of past outputs, and `su`

is the number
of past inputs that are used for the predictions. See pages 209 and
210 in [3] for
more information. These numbers can have a substantial influence on
the quality of the resulting model, and there are no simple rules
for choosing them. Making `'N4Horizon'`

a `k`

-by-3
matrix means that each row of `'N4Horizon'`

is tried,
and the value that gives the best (prediction) fit to data is selected. `k`

is
the number of guesses of ` [r sy su]`

combinations. If you specify N4Horizon
as a single column, `r = sy = su`

is used.

`'auto'`

— The software uses
an Akaike Information Criterion (AIC) for the selection of `sy`

and `su`

.

Estimation focus that defines how the errors *e* between
the measured and the modeled outputs are weighed at specific frequencies
during the minimization of the prediction error, specified as one
of the following:

`'prediction'`

— Automatically
calculates the weighting function as a product of the input spectrum
and the inverse of the noise spectrum. The weighting function minimizes
the one-step-ahead prediction. This approach typically favors fitting
small time intervals (higher frequency range). From a statistical-variance
point of view, this weighting function is optimal. However, this method
neglects the approximation aspects (bias) of the fit.

This option focuses on producing a good predictor and does not
enforce model stability. Use `'stability'`

when you
want to ensure a stable model.

`'simulation'`

— Estimates
the model using the frequency weighting of the transfer function that
is given by the input spectrum. Typically, this method favors the
frequency range where the input spectrum has the most power. This
method provides a stable model.

`'stability'`

— Same as `'prediction'`

,
but with model stability enforced.

Passbands — Row vector or matrix containing
frequency values that define desired passbands. For example:

[wl,wh]
[w1l,w1h;w2l,w2h;w3l,w3h;...]

where `wl`

and `wh`

represent
lower and upper limits of a passband. For a matrix with several rows
defining frequency passbands, the algorithm uses union of frequency
ranges to define the estimation passband.

Passbands are expressed in `rad/TimeUnit`

for
time-domain data and in `FrequencyUnit`

for frequency-domain
data, where `TimeUnit`

and `FrequencyUnit`

are
the time and frequency units of the estimation data.

SISO filter — Specify a SISO linear filter
in one of the following ways:

A single-input-single-output (SISO) linear system

`{A,B,C,D}`

format, which specifies
the state-space matrices of the filter

`{numerator, denominator}`

format,
which specifies the numerator and denominator of the filter transfer
function

This option calculates the weighting function as a product of
the filter and the input spectrum to estimate the transfer function.
To obtain a good model fit for a specific frequency range, you must
choose the filter with a passband in this range. The estimation result
is the same if you first prefilter the data using `idfilt`

.

Weighting vector — For frequency-domain data
only, specify a column vector of weights. This vector must have the
same length as the frequency vector of the data set, `Data.Frequency`

.
Each input and output response in the data is multiplied by the corresponding
weight at that frequency.

Controls whether parameter covariance data is generated, specified
as `true`

or `false`

.

If `EstCovar`

is `true`

,
then use `getcov`

to fetch the
covariance matrix from the estimated model.

Specify whether to display the estimation progress, specified
as one of the following strings:

Removal of offset from time-domain input data during estimation,
specified as the comma-separated pair consisting of `'InputOffset'`

and
one of the following:

A column vector of positive integers of length *Nu*,
where *Nu* is the number of inputs.

`[]`

— indicates no offset

*Nu*-by-*Ne* matrix
— For multiexperiment data, specify `InputOffset`

as
an *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.

Removal of offset from time domain output data during estimation,
specified as the comma-separated pair consisting of `'OutputOffset'`

and
one of the following:

A column vector of length *Ny*, where *Ny* is
the number of outputs.

`[]`

— indicates no offset

*Ny*-by-*Ne* matrix
— 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.

Specifies criterion used during minimization, specified as one
of the following:

`'noise'`

— Minimize $$\mathrm{det}(E\text{'}*E)$$, where *E* represents
the prediction error. This choice is optimal in a statistical sense
and leads to the maximum likelihood estimates in case no data is available
about the variance of the noise. This option uses the inverse of the
estimated noise variance as the weighting function.

Positive semidefinite symmetric matrix (`W`

)
— Minimize the trace of the weighted prediction error matrix `trace(E'*E*W)`

. `E`

is
the matrix of prediction errors, with one column for each output. `W`

is
the positive semidefinite symmetric matrix of size equal to the number
of outputs. Use `W`

to specify the relative importance
of outputs in multiple-input, multiple-output models, or the reliability
of corresponding data.

This option is relevant only for multi-input, multi-output models.

`[]`

— The software chooses
between the `'noise'`

or using the identity matrix
for `W`

.

`Advanced`

is a structure with the field `MaxSize`

. `MaxSize`

specifies
the maximum number of elements in a segment when input-output data
is split into segments.

`MaxSize`

must be a positive integer.

**Default:** 250000