LoadSQW dialog.
Table of Contents
Create a MDEventWorkspace with events in reciprocal space (Qx, Qy, Qz, Energy) from a SQW file.
| Name | Direction | Type | Default | Description |
|---|---|---|---|---|
| Filename | Input | string | Mandatory | File of type SQW format. Allowed extensions: [‘.sqw’] |
| OutputWorkspace | Output | MDEventWorkspace | Mandatory | Output IMDEventWorkspace reflecting SQW data read-in. |
| MetadataOnly | Input | boolean | False | Load Metadata without events. |
| OutputFilename | Input | string | If the input SQW file is too large to fit in memory, specify an output NXS file. The MDEventWorkspace will be create with this file as its back-end. Allowed extensions: [‘.nxs’] |
The algorithm takes every pixel defined in the SQW horace file and converts it into an event.
Only top level binning information is currently taken from DND/Image
data. All DND image information is currently ignored and the resulting
MDEvent workspace is in the units of 
(SQW dimensions,
recalculated to the Crystal? frame, without HKL transformation).
U matrix is set to unity but the B-matrix is read from the SQW and attached to the workspace which may confuse the algorithms which work with MDEventWorkspace produced by Mantid algorithms.
Sqw objects comes in two flavours:
The former has the four main fields fully filled. The fields description is given below. The latter has:
The dnd-type is created from d0d, d1d,... objects for most algorithms so as to use private methods of sqw objects.
DND-type object can not be currently read or understood by Mantid.
String started by:
% -- ignored
* -- used
Main_header:
% main_headerfilename Name of sqw file that is being read, excluding path
% main_headerfilepath Path to sqw file that is being read, including terminating file separator
% main_headertitle Title of sqw data structure
% main_headernfiles Number of spe files that contribute to the sqw object
Header: (scalar structure, or cellarray of scalar structures if more than one spe file)
% header{i}.filename Name of sqw file excluding path
% header{i}.filepath Path to sqw file including terminating file separator
% header{i}.efix Fixed energy (ei or ef depending on emode)
% header{i}.emode Emode=1 direct geometry, =2 indirect geometry, =0 if diffraction ''' Only emode 1 have ever been tried '''
% header{i}.alatt Lattice parameters (Angstroms)
% header{i}.angdeg Lattice angles (deg)
% header{i}.cu First vector defining scattering plane (r.l.u.)
% header{i}.cv Second vector defining scattering plane (r.l.u.)
% header{i}.psi Orientation angle (rad)
% header{i}.omega --|
% header{i}.dpsi | Crystal misorientation description (rad)
% header{i}.gl | (See notes elsewhere e.g. Tobyfit manual
% header{i}.gs --|
% header{i}.en Energy bin boundaries (meV) in the input spe file [column vector]
% header{i}.uoffset Offset of origin of pixel projection axes in r.l.u. and energy i.e. [h; k; l; en] [column vector]
% header{i}.u_to_rlu Matrix (4x4) of pixel projection axes in hkle representation
% u(:,1) first vector - u(1:3,1) r.l.u., u(4,1) energy etc.
% header{i}.ulen Length of pixel projection axes vectors in Ang^-1 or meV [row vector]
% header{i}.ulabel Labels of the pixel projection axes [1x4 cell array of character strings]
The pixel projection axes, u1, u2, u3 are the orthonormal vectors of the crystal Cartesian coordinate frame i.e. u1 || a*, u2 in plane of a*, and b*, and u3 || a* x b*. They form the coordinate frame in which the pixel coordinates are stored in data.pix. The pixel projection axes must necessarily be identical for all contributing spe files.
\ **Detpar**\ :
% detpar.filename Name of file excluding path
% detpar.filepath Path to file including terminating file separator
% detpar.group Row vector of detector group number
% detpar.x2 Row vector of secondary flightpaths (m)
% detpar.phi Row vector of scattering angles (deg)
% detpar.azim Row vector of azimuthal angles (deg)
% (West bank=0 deg, North bank=90 deg etc.)
% detpar.width Row vector of detector widths (m)
% detpar.height Row vector of detector heights (m)
\ **Data**\ :
% data.filename Name of sqw file that is being read, excluding path
% data.filepath Path to sqw file that is being read, including terminating file separator
% data.title Title of sqw data structure
* data.alatt Lattice parameters for data field (Ang^-1)
* data.angdeg Lattice angles for data field (degrees)
% data.uoffset Offset of origin of projection axes in r.l.u. and energy ie. [h; k; l; en] [column vector]
% data.u_to_rlu Matrix (4x4) of projection axes in hkle representation
% u(:,1) first vector - u(1:3,1) r.l.u., u(4,1) energy etc.
% data.ulen Length of projection axes vectors in Ang^-1 or meV [row vector]
% data.ulabel Labels of the projection axes [1x4 cell array of character strings]
% data.iax Index of integration axes into the projection axes [row vector]
% Always in increasing numerical order
% e.g. if data is 2D, data.iax=[1,3] means summation has been performed along u1 and u3 axes
% data.iint Integration range along each of the integration axes. [iint(2,length(iax))]
% e.g. in 2D case above, is the matrix vector [u1_lo, u3_lo; u1_hi, u3_hi]
% data.pax Index of plot axes into the projection axes [row vector]
% Always in increasing numerical order
% e.g. if data is 3D, data.pax=[1,2,4] means u1, u2, u4 axes are x,y,z in any plotting
% 2D, data.pax=[2,4] " u2, u4, axes are x,y in any plotting
% data.p Call array containing bin boundaries along the plot axes [column vectors]
% i.e. row cell array {data.p{1}, data.p{2} ...} (for as many axes as length of data.pax)
% data.dax Index into data.pax of the axes for display purposes. For example we may have
% data.pax=[1,3,4] and data.dax=[3,1,2] This means that the first display axis is data.pax(3)=4,
% the second is data.pax(1)=1, the third is data.pax(2)=3. The reason for data.dax is to allow
% the display axes to be permuted but without the contents of the fields p, s,..pix needing to
% be reordered [row vector]
-----> Large data fields, data for MD image
% data.s Cumulative signal. [size(data.s)=(length(data.p1)-1, length(data.p2)-1, ...)]
% data.e Cumulative variance [size(data.e)=(length(data.p1)-1, length(data.p2)-1, ...)]
% data.npix No. contributing pixels to each bin of the plot axes.
% [size(data.pix)=(length(data.p1)-1, length(data.p2)-1, ...)]
----->
* data.urange True range of the data along each axis [urange(2,4)]
----> Pixels or events data
* data.pix Array containing data for each pixel:
* If npixtot=sum(npix), then pix(9,npixtot) contains:
* u1 -|
* u2 | Coordinates of pixel in the pixel projection axes
* u3 |
* u4 -|
* irun Run index in the header block from which pixel came
* idet Detector group number in the detector listing for the pixel
* ien Energy bin number for the pixel in the array in the (irun)th header
* signal Signal array
* err Error array (variance i.e. error bar squared)
data.s is normalized by the number of pixels, as is the variance data.e. For those elements where data.npix==0, data.s=0 and data.e=0
Parts of the code were written with the idea of generalising functionality at a later stage. However, we can now assume that:
Note
To run these usage examples please first download the usage data, and add these to your path. In MantidPlot this is done using Manage User Directories.
Example - Load 4D workspace form sample SQW file.
# Delete existing workspace if it is already in Mantid as LoadSQW does not support overwriting
# existig workspaces by design
if 'mdws' in mtd:
DeleteWorkspace('mdws')
#
# Load sample sqw file, present in Mantid unit tests as MD workspace
mdws = LoadSQW('test_horace_reader.sqw');
# Check results
print "Workspace type is: ",mdws.id()
print "Workspace has:{0:2} dimensions and contains: {1:4} MD events".format(mdws.getNumDims(),mdws.getNEvents())
Output:
Workspace type is: MDEventWorkspace<MDEvent,4>
Workspace has: 4 dimensions and contains: 580 MD events
Categories: Algorithms | DataHandling | MDAlgorithms