System Identification Toolbox

size

Dimensions of iddata. idfrd and idmodel 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)
  

Description

size describes the dimensions of both model and iddata objects.

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

N = the length of the data record. For multiexperiment 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 just one of these sizes use size(data,k) for the k-th dimension or size(data,'N'), size(data,'ny'), etc.

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

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 (= the number of estimated parameters)

Nx = the number of states for idss and idgrey models.

Also in this case the individual dimensions are obtained by size(mod,2), size(mod,'Npar'), etc.

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

[ny nu Npar]

For idfrd models, the sizes are:

ny = number of output channels

nu = number of input channels

Nf = number of frequencies

Ns = number of spectrum channels

Also in this case the individual dimensions are obtained by size(mod,2), size(mod,'Nf'), etc.

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

• [ny nu Nf]
  

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

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