optimget

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optimget — Queries an optimization data structure.

SYNOPSIS

      val = optimget ( options , key )
      val = optimget ( options , key , value )

Description

This function allows to make queries on an existing optimization data structure. This data structure must have been created and updated by the optimset function. The optimget allows to retrieve the value associated with a given key.

In the following, we analyse the various ways to call the optimget function.

The following calling sequence

 
val = optimget(options , key)

returns the value associated with the given key. The key is expected to be a string. We search the key among the list of all possible fields in the options data structure. In this search, the case is ignored. The key which matches a possible field is returned. Some letters of the field may be dropped, provided that the matching field is unique. For example, the key "MaxF" corresponds to the field "MaxFunEval". But the key "Tol" corresponds both to the "TolX" and "TolFun" fields and therefore will generate an error.

The following calling sequence

 
val = optimget(options, key, value)

allows to manage default value for optimization parameters. Indeed, if the field corresponding to the key is empty (i.e. has not been set by the user), the input argument value is returned. Instead, if the field corresponding the the key is not empty (i.e. has been set by the user), the parameter stored in the options argument is returned.

Parameters

options: A struct which contains the optimization fields.
key: A string corresponding to a field of the optimization structure.
value: A real default value.
val: The real value corresponding to the key.

Example #1

In the following example, we create an optimization structure and set the "TolX" field to 1.e-12. Then we use optimget to get back the value.

 
op = optimset();
op = optimset(op,'TolX',1.e-12);
val = optimget(op,'TolX'); // val is 1.e-12

Example #2

In the following example, we create an empty optimization structure. Then we use optimget to get back the value corresponding to the "TolX" field, with 1.e-5 as the default value. Since the field is empty, we retrieve 1.e-5.

 
op = optimset();
val = optimget(op,'TolX' , 1.e-5); // val = 1.e-5

Example #3

In the following example, we create an optimization structure and set the "TolX" field to 1.e-12. Then we use optimget to get back the value corresponding to the "TolX" field, with 1.e-5 as the default value. Since the field is not empty, we retrieve 1.e-12.

 
op = optimset();
op = optimset(op,'TolX',1.e-12);
val = optimget(op,'TolX' , 1.e-5); // val = 1.e-12

Example #4

In the following example, we create an optimization structure and configure the maximum number of function evaluations to 1000. Then we quiery the data structure, giving only the "MaxF" key to the optimget function. Since that corresponds only to the "MaxFunEvals" field, there is only one match and the function returns 10000.

 
op = optimset();
op = optimset(op, 'MaxFunEvals' , 1000);
val = optimget(op, 'MaxF'); // val = 1000

Authors

Michael Baudin - Digiteo - 2009

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