question: public double [ ] extractEquationData ( final int index , final double [ ] complete ) throws MathIllegalArgumentException { checkIndex ( index ) ; final int begin = start [ index ] ; final int end = start [ index + 1 ] ; if ( complete . length < end ) { throw new MathIllegalArgumentException ( LocalizedCoreFormats . DIMENSIONS_MISMATCH , complete . length , end ) ; } final int dimension = end - begin ; final double [ ] equationData = new double [ dimension ] ; System . arraycopy ( complete , begin , equationData , 0 , dimension ) ; return equationData ; }
target:  Extract equation data from a complete state or derivative array.