idParametric/getpar

Obtain attributes such as values and bounds of linear model parameters

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Syntax

value = getpar(sys,'value')
free = getpar(sys,'free')
bounds = getpar(sys,'bounds')
label = getpar(sys,'label')
getpar(sys)

Description

example

value = getpar(sys,'value') returns the parameter values of the model sys. If sys is a model array, the returned value is a cell array of size equal to the model array.

example

free = getpar(sys,'free') returns the free or fixed status of the parameters.

example

bounds = getpar(sys,'bounds') returns the minimum and maximum bounds on the parameters.

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label = getpar(sys,'label') returns the labels for the parameters.

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getpar(sys) prints a table of parameter values, labels, free status and minimum and maximum bounds.

Examples

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Open Live Script

Get the parameter values of an estimated ARMAX model.

Estimate an ARMAX model. 

load iddata8
init_data = z8(1:100);
na = 1;
nb = [1 1 1];
nc = 1;
nk = [0 0 0];
sys = armax(init_data,[na nb nc nk]);

Get the parameter values. 

val = getpar(sys,'value')
val = 5×1

   -0.7519
   -0.4341
    0.4442
    0.0119
    0.3431

To set parameter values, use sys = setpar(sys,'value',value).

Open Live Script

Get the free parameters and their bounds for a process model.

Construct a process model, and set its parameter values and free status. 

m = idproc('P2DUZI');
m.Kp = 1;
m.Tw = 100;
m.Zeta = .3;
m.Tz = 10;
m.Td = 0.4;
m.Structure.Td.Free = 0;

Here, the value of Td is fixed.

Get the parameter values. 

Val = getpar(m,'Value')
Val = 5×1

    1.0000
  100.0000
    0.3000
    0.4000
   10.0000

Get the free statuses of the parameters. 

Free = getpar(m,'Free')
Free = 5x1 logical array

   1
   1
   1
   0
   1

The output indicates that Td is a fixed parameter and the remaining parameters are free.

Get the default bounds on the parameters. 

MinMax = getpar(m,'bounds')
MinMax = 5×2

  -Inf   Inf
     0   Inf
     0   Inf
     0   Inf
  -Inf   Inf

Extract the values of the free parameters. 

FreeValues = Val(Free)
FreeValues = 4×1

    1.0000
  100.0000
    0.3000
   10.0000

Extract the bounds on the free parameters. 

FreeValBounds = MinMax(Free,:)
FreeValBounds = 4×2

  -Inf   Inf
     0   Inf
     0   Inf
  -Inf   Inf
Open Live Script

Get the parameter labels of an estimated ARMAX model.

Estimate an ARMAX model. 

load iddata8;
init_data = z8(1:100);
na = 1;
nb = [1 1 1];
nc = 1;
nk = [0 0 0];
sys = armax(init_data,[na nb nc nk]);

Assign parameter labels. 

sys.Structure.A.Info(2).Label = 'a2';

Get the parameter labels. 

label = getpar(sys,'label')
label = 5x1 cell
    {'a2'    }
    {0x0 char}
    {0x0 char}
    {0x0 char}
    {0x0 char}
Open Live Script

Obtain a table of all model parameter attributes of an ARMAX model.

Estimate an ARMAX model. 

load iddata8;
init_data = z8(1:100);
na = 4;
nb = [3 2 3];
nc = 2;
nk = [0 0 0];
sys = armax(init_data,[na nb nc nk]);

Get all parameter attributes. 

getpar(sys)
------------------------------------------------------
  #  Label     Value   Free       Min.         Max.   
------------------------------------------------------
  1.         -1.4328    1       -Inf          Inf
  2.           0.497    1       -Inf          Inf
  3.         0.22904    1       -Inf          Inf
  4.        -0.09849    1       -Inf          Inf
  5.        -0.10246    1       -Inf          Inf
  6.          1.1671    1       -Inf          Inf
  7.         0.39579    1       -Inf          Inf
  8.         0.97219    1       -Inf          Inf
  9.        0.026995    1       -Inf          Inf
 10.        -0.17113    1       -Inf          Inf
 11.         0.16155    1       -Inf          Inf
 12.         0.48468    1       -Inf          Inf
 13.         -1.8871    1       -Inf          Inf
 14.         0.97391    1       -Inf          Inf

Input Arguments

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Identified linear model, specified as an idss, idpoly, idgrey, idtf, or idfrd model object or an array of model objects.

Output Arguments

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Parameter values, returned as a double vector of length nparams(sys).

Free or fixed status of parameters, returned as a logical vector of length nparams(sys).

Minimum and maximum bounds on parameters, returned as a double matrix of size nparams(sys)-by-2. The first column contains the minimum bound, and the second column the maximum bound.

Parameter labels, returned as a cell array of character vectors of length nparams(sys). For example, {'a2','a3'}, if nparams(sys) is two.

See Also

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Introduced in R2013b

System Identification Toolbox Documentation

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