System Identification Toolbox™

size - Dimensions of `iddata`, `idmodel`, `idnlmodel`, and `idfrd` objects

Syntax

d = size(m)
[ny,nu,Npar,Nx] = size(model)
[N, ny, nu, Nexp] = size(data)
ny = size(data,2)
ny = size(data,'ny')
size(model)
size(idfrd_object)

Description

size describes the dimensions of iddata, idmodel, idnlmodel, and idfrd objects.

iddata

For iddata objects, the sizes returned are, in this order,

N = the length of the data record. For multiple-experiment data, N is a row vector with as many entries as there are experiments.
ny = the number of output channels.
ny = the number of input channels.
Ne = the number of experiments.

To access a specific size output, use syntax similar to the following: size(data,k) for the k size(data,'N'),size(data,'ny').

When called with one output argument, d = size(data) returns

d = [N ny nu] if the number of experiments is 1.
d = [sum(N) ny nu Ne] if the number of experiments is Ne > 1.

idmodel

For idmodel objects the sizes returned are, in this order,

ny = the number of output channels.
nu = the number of input channels.
Npar = the length of the ParameterVector (number of estimated parameters).
Nx = the number of states for idss and idgrey models.

To access a specific size output, use syntax similar to the following: size(mod,2), size(mod,'Npar').

When size is called with one output argument, d = size(mod), d is given by

 [ny nu Npar]

idfrd

For idfrd models, the sizes returned are, in this order,

ny = the number of output channels.
nu = the number of input channels.
Nf = the number of frequencies.
Ns = the number of spectrum channels.

To access a specific size output, use syntax similar to the following: size(mod,2) or size(mod,'Nf').

When size is called with one output argument, d = size(fre), d is given by

[ny nu Nf Ns]

When size is called with no output arguments, in any of these cases, the information is displayed in the MATLAB Command Window.

idnlarx or idnlhw

For idmodel objects the sizes returned are, in this order,

ny = the number of output channels.
nu = the number of input channels.

To access a specific size output, use one of the following:

NY = SIZE(NLSYS,1)
NU = SIZE(NLSYS,2)
NY = SIZE(NLSYS,'Ny')
NU = SIZE(NLSYS,'Nu')

When called with only one output argument, N = SIZE(NLSYS) returns the vector N = [NY NU].

When called with no output argument, the information is displayed in the MATLAB Command Window.

idnlgrey

For idnlgrey objects the sizes returned are, in this order,

Ny = the number of output channels.
Nu = the number of input channels.
Nx = the number of states.
Np = the number of parameters.
Npo = the number of parameter variables (number of estimated parameters).
Npf = the number of fixed parameters.
Ne = the number of experiments associated with the states.

Ny, Nu, Nx, Np,Npo, Npf and Ne are set to NaN if NLSYS is inconsistent.