Function Reference

size

Provide the output/input/array dimensions of LTI models, the model order of TF, SS, and ZPK models, and the number of frequencies of FRD models

Syntax

• size(sys)
  d = size(sys)
  Ny = size(sys,1)
  Nu = size(sys,2)
  Sk = size(sys,2+k)
  Ns = size(sys,'order')
  Nf = size(sys,'frequency')
  

Description

When invoked without output arguments, size(sys) returns a vector of the number of outputs and inputs for a single LTI model. The lengths of the array dimensions are also included in the response to size when sys is an LTI array. size is the overloaded version of the MATLAB function size for LTI objects.

d = size(sys) returns:

• The row vector d = [Ny Nu] for a single LTI model sys with Ny outputs and Nu inputs
• The row vector d = [Ny Nu S1 S2 ... Sp] for an S1-by-S2-by-...-by-Sp array of LTI models with Ny outputs and Nu inputs

Ny = size(sys,1) returns the number of outputs of sys.

Nu = size(sys,2) returns the number of inputs of sys.

Sk = size(sys,2+k) returns the length of the k-th array dimension when sys is an LTI array.

Ns = size(sys,'order') returns the model order of a TF, SS, or ZPK model. This is the same as the number of states for state-space models. When sys is an LTI array, ns is the maximum order of all of the models in the LTI array.

Nf = size(sys,'frequency') returns the number of frequencies when sys is an FRD. This is the same as the length of sys.frequency.

Example

Consider the random LTI array of state-space models

• sys = rss(5,3,2,3);
  

Its dimensions are obtained by typing

• size(sys)
  3x1 array of state-space models
  Each model has 3 outputs, 2 inputs, and 5 states.
  

See Also
isempty     Test if LTI model is empty

issiso      Test if LTI model is SISO

ndims       Number of dimensions of an LTI array

sisotool

sminreal