# Check Cost Function

### Description

This function checks that the cost function is correctly specified in the
optimization object, including that the elements of `this`

used by the
cost function are consistent.

### Usage

1 | ```
optimbase.checkcostfun(this = NULL)
``` |

### Arguments

`this` |
An optimization object |

### Details

Depending on the definition of nonlinear constraints (`nbineqconst`

element > 0) and the use of derivatives (`withderivatives`

element set to
TRUE), this function makes several cost function calls with different
`index`

value (see `vignette('optimbase',package='optimbase')`

for
more details about `index`

). If at least one call fails, the function
stops the search algorithm.

Following every successful cost function call, `optimbase.checkcostfun`

calls `optimbase.checkshape`

to check the dimensions of the matrix
returned by the cost function against some expectations.

### Value

Return the optimization object or an error message if one check is not successful.

### Author(s)

Author of Scilab optimbase module: Michael Baudin (INRIA - Digiteo)

Author of R adaptation: Sebastien Bihorel (sb.pmlab@gmail.com)

### See Also

`optimbase.checkshape`