clipper::MapFilter_fft< T > Class Template Reference

Simple fft-based radial mapfiltering implementation. More...

#include <mapfilter.h>

Inheritance diagram for clipper::MapFilter_fft< T >:

List of all members.

Public Types
enum	TYPE { NONE, Absolute, Relative }
	Scaling modes.
Public Member Functions
	MapFilter_fft (const MapFilterFn_base &fltr, const ftype scale=1.0, const TYPE type=NONE)
	constructor
	MapFilter_fft (clipper::Xmap< T > &result, const clipper::Xmap< T > &xmap, MapFilterFn_base &fltr, const ftype scale=1.0, const TYPE type=NONE)
	constructor: shorthand for constructor+operator
bool	operator() (clipper::Xmap< T > &result, const clipper::Xmap< T > &xmap) const
bool	operator() (clipper::NXmap< T > &result, const clipper::NXmap< T > &nxmap) const

---

Detailed Description

template<class T>
class clipper::MapFilter_fft< T >

Simple fft-based radial mapfiltering implementation.

The FFT method is fast, and also gives good precision.

The following example demonstrates how to use the MapFilter to calculate the local mean and local deviation of an electron density map, in 'xmap':

 make squared map
    clipper::Xmap<float> xmap2( xmap );
    clipper::Xmap<float>::Map_reference_index ix;
    for ( ix = xmap2.first(); !ix.last(); ix.next() )
      xmap2[ix] = pow( xmap2[ix], 2.0 );

 now calculate local mean, local mean squared
    clipper::MapFilterFn_step fn( filter_radius );
    clipper::MapFilter_fft<float> fltr( fn, 1.0, clipper::MapFilter_fft<float>::Relative );
    clipper::Xmap<float> lmean, lsigm;
    fltr( lmean, xmap );
    fltr( lsigm, xmap2 );

 calculate std deviation
    for ( ix = lmean.first(); !ix.last(); ix.next() )
      lsigm[ix] = sqrt( lsigm[ix] - pow( lmean[ix], 2.0 ) );

This would be a useful step in solvent mask determination, for example.

---

Constructor & Destructor Documentation

template<class T >

clipper::MapFilter_fft< T >::MapFilter_fft	(	const MapFilterFn_base &	fltr,
		const ftype	scale = 1.0,
		const TYPE	type = NONE
	)			[inline]

constructor

The filter function is constructed with the given filter. Scaling may also be optionally applied. This may be absolute, which just applies a scale factor to the result, or relative, which scales the filter relative to its own integral. Therefore, relative scaling with a scale factor of 1.0 gives an output map on the same scale as the input map.

Note that the filter is not stored internally, and so must persist as long as the MapFilter is required.

Parameters:

	fltr	The radial filter to apply.
	scale	The scale factor to apply (default = 1.0).
	type	The type of scaling to apply: NONE, Absolute, Relative.

---

Member Function Documentation

template<class T >

bool clipper::MapFilter_fft< T >::operator()	(	clipper::Xmap< T > &	result,
		const clipper::Xmap< T > &	xmap
	)			const [inline, virtual]

Apply the filter to a given map.

Parameters:

	result	The filtered map.
	xmap	The map to be filtered.

Implements clipper::MapFilter_base< T >.

References clipper::Xmap< T >::cell(), clipper::Xmap_base::Map_reference_coord::coord(), clipper::Coord_grid::coord_frac(), clipper::FFTmap_p1::cplx_data(), clipper::FFTmap_p1::fft_x_to_h(), clipper::Xmap< T >::first(), clipper::Xmap< T >::grid_sampling(), clipper::Xmap< T >::init(), clipper::Coord_frac::lengthsq(), clipper::Xmap_base::Map_reference_coord::next_u(), clipper::Xmap_base::Map_reference_coord::next_v(), clipper::Xmap_base::Map_reference_coord::next_w(), clipper::Grid::nu(), clipper::Grid_sampling::nu(), clipper::Grid::nv(), clipper::Grid_sampling::nv(), clipper::Grid::nw(), clipper::Grid_sampling::nw(), clipper::FFTmap_p1::real_data(), clipper::Xmap< T >::spacegroup(), clipper::Coord_grid::u(), clipper::Coord_grid::v(), clipper::Cell::volume(), and clipper::Coord_grid::w().

template<class T >

bool clipper::MapFilter_fft< T >::operator()	(	clipper::NXmap< T > &	result,
		const clipper::NXmap< T > &	nxmap
	)			const [inline]

Apply the filter to a given map.

Parameters:

	result	The filtered map.
	nxmap	The map to be filtered.

References clipper::FFTmap_p1::cplx_data(), clipper::FFTmap_p1::fft_x_to_h(), clipper::NXmap< T >::first(), clipper::NXmap< T >::grid(), clipper::NXmap< T >::init(), clipper::Grid_sampling::nu(), clipper::Grid::nu(), clipper::Grid_sampling::nv(), clipper::Grid::nv(), clipper::Grid_sampling::nw(), clipper::Grid::nw(), clipper::NXmap< T >::operator_grid_orth(), clipper::NXmap< T >::operator_orth_grid(), clipper::FFTmap_p1::real_data(), clipper::RTop< T >::rot(), clipper::Coord_grid::u(), clipper::Coord_grid::v(), clipper::Coord_grid::w(), and clipper::Vec3<>::zero().

---

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

• mapfilter.h
• mapfilter.cpp