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# optimget

Queries an optimization data structure.

### Syntax

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 syntax

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 syntax

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 key is not empty
(i.e. has been set by the user), the parameter stored in the `options`

argument is returned.

### Arguments

- 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.

### 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.

### Example #4

In the following example, we create an optimization structure and
configure the maximum number of function evaluations to 1000. Then we
query 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.

### See also

- optimset — Configures and returns an optimization data structure.

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