2nd order resolution function evaluator More...

#include <resol_fn.h>

Inheritance diagram for clipper::ResolutionFn:

Public Member Functions
	ResolutionFn (const HKL_info &hkl_info, const BasisFn_base &basisfn, const TargetFn_base &targetfn, const std::vector< ftype > &params, const ftype damp=0.0, const bool debug=false)
	constructor: need reflections, basis fn and target fn.
ftype	f (const HKL_info::HKL_reference_index &ih) const
	return the value of the basis function with the current paramters
const std::vector< ftype > &	params () const
	return the values of the parameters
void	debug () const
	print the target, gradient, and curvatures with respect to the params
Protected Member Functions
void	calc_derivs (const std::vector< ftype > &params, ftype &r, std::vector< ftype > &drdp, Matrix<> &drdp2) const
	calculate derivatives of target wrt params
	ResolutionFn ()
	null constructor
Protected Attributes
const HKL_info *	hkl_info_
	reflection list
const TargetFn_base *	targetfn_
	target function
const BasisFn_base *	basisfn_
	basis function
std::vector< ftype >	params_
	basis function parameters
Cell	cell_
	cell

Detailed Description

2nd order resolution function evaluator

This is an automatic evaluator for arbitrary functions of HKL, most commonly used for evaluating a function of resolution (such a mean F^2 or sigmaa), although more general tasks including local scaling of reflections and anisotropic functions can also be handled. This form is for target functions which approach zero quadratically, e.g. least-squares targets.

This version implements a naive Newton-Raphson minimiser, which only uses the gradient and curvature of the target function, ignoring its value. It is ideal for quadratic targets with linear basis functions.

To evaluate a resolution function, this class must be provided with two objects:

The basis function (and gradients), which describes the value of the function for any reflection given a set of paramters.
The target function (and derivatives), which is used to determine the values of the basis function parameters.

For example, the following code may be used to calculate a smooth scaling function to scale one set of data to another using an anisotropic Gaussian scaling function:

    // make data object
    clipper::HKL_info hkls;
    clipper::HKL_data<clipper::data32::F_sigF> fsig1( hkls );
    clipper::HKL_data<clipper::data32::F_sigF> fsig2( hkls );
    // INITIALISE THEM HERE!

    // calculate the scaling function
    std::vector<clipper::ftype> params( 7, 0.0 );  // initial parameters
    clipper::BasisFn_aniso_gaussian basisfn;       // aniso gaussian
    clipper::TargetFn_scaleF1F2<clipper::data32::F_sigF,clipper::data32::F_sigF>targetfn( fsig1, fsig2 );
    clipper::ResolutionFn_nonlinear rfn( hkls, basisfn, targetfn, params );

    // now scale the data
    clipper::HKL_info::HKL_reference_index ih;
    for ( ih = hkls.first(); !ih.last(); ih.next() )
      fsig1[ih].scale( sqrt( rfn.f(ih) ) );

The most useful isotropic resolution function is the BasisFn_spline, since it is linear and provides a good fit to most data.

Constructor & Destructor Documentation

clipper::ResolutionFn::ResolutionFn	(	const HKL_info &	hkl_info,
		const BasisFn_base &	basisfn,
		const TargetFn_base &	targetfn,
		const std::vector< ftype > &	params,
		const ftype	damp = `0.0`,
		const bool	debug = `false`
	)

constructor: need reflections, basis fn and target fn.

The constructor performs the full minimisation calculation.

Parameters:

hkl_info	HKL_info object which provides the reflection list.
basisfn	The basis function used to describe the desired property.
targetfn	The target function to be minimised.
params	Initial values for the function parameters.
damp_	If > 0.0, shifts are fdamped during early cycles to help convergence with difficult bases/target conbinations.

References basisfn_, calc_derivs(), clipper::HKL_info::cell(), cell_, hkl_info_, clipper::BasisFn_base::num_params(), params(), params_, clipper::Matrix< T >::solve(), targetfn_, clipper::TargetFn_base::type(), and clipper::BasisFn_base::type().

Member Function Documentation

const std::vector< ftype > & clipper::ResolutionFn::params ( ) const

return the values of the parameters

Returns:: The refined basis function parameters

References params_.

Referenced by calc_derivs(), ResolutionFn(), and clipper::ResolutionFn_nonlinear::ResolutionFn_nonlinear().

void clipper::ResolutionFn::calc_derivs	(	const std::vector< ftype > &	params,
		ftype &	r,
		std::vector< ftype > &	drdp,
		Matrix<> &	drdp2
	)		const `[protected]`

calculate derivatives of target wrt params

The target and its derivatives are calculated by the chain rule and accumulated over all HKLs.

Parameters:

params	Current value of parameters.
r	The value of the target function.
drdp	The derivative of the target function.
drdp2	The curvature of the target function.

References basisfn_, cell_, clipper::BasisFn_base::Fderiv::df, clipper::BasisFn_base::Fderiv::df2, clipper::TargetFn_base::Rderiv::dr, clipper::TargetFn_base::Rderiv::dr2, clipper::HKL_class::epsilonc(), f(), clipper::BasisFn_base::fderiv(), clipper::HKL_info::first(), clipper::HKL_info::HKL_reference_index::hkl(), clipper::HKL_info::HKL_reference_index::hkl_class(), hkl_info_, clipper::HKL_info::HKL_reference_index::last(), clipper::Util::max(), clipper::Util::min(), clipper::HKL_info::HKL_reference_index::next(), clipper::BasisFn_base::num_diagonals(), clipper::BasisFn_base::num_params(), params(), clipper::TargetFn_base::Rderiv::r, clipper::TargetFn_base::rderiv(), and targetfn_.

Referenced by ResolutionFn(), and clipper::ResolutionFn_nonlinear::ResolutionFn_nonlinear().

The documentation for this class was generated from the following files:

resol_fn.h
resol_fn.cpp

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation