3.6

LoadFlexiNexus v1

../_images/LoadFlexiNexus-v1_dlg.png

LoadFlexiNexus dialog.

Summary

Loads a NeXus file directed by a dictionary file

Properties

Name Direction Type Default Description
Filename Input string Mandatory A NeXus file. Allowed values: [‘.hdf’, ‘.h5’, ‘’]
Dictionary Input string Mandatory A Dictionary for controlling NeXus loading. Allowed values: [‘.txt’, ‘.dic’, ‘’]
OutputWorkspace Output Workspace Mandatory  

Description

This algorithm is a flexible NeXus file loader. Data loading is driven by a dictionary. Correspondingly the algorithm takes as arguments: a filename, a path to a dictionary file and an output workspace name.

The dictionary itself is a list of key=value pairs, one per line. Normally dictionary entries take the form key-path-into-Nexus-file. The default action is to store the data found at path-into-NeXus-file under key key in the Run information of the result workspace. But some keys are interpreted specially:

data=path-into-nexus-file
This is a required entry. path-into-nexus-file is the path in the NeXus file to the data which is the main bulk workspace data. Usually the counts. From the dimensionality of this data the type of result workspace is determined. If the rank is <= 2, then a Workspace2D is created, else a MDHistoWorkspace.
x-axis=path-into-nexus-file
The data found under the path into the NeXus file will be used as axis 0 on the dataset
x-axis-name=text
The text specified will become the name of the axis 0
y-axis=path-into-nexus-file
The data found under the path into the NeXus file will be used as axis 1 on the dataset
y-axis-name=text
The text specified will become the name of the axis 1
z-axis=path-into-nexus-file
The data found under the path into the NeXus file will be used as axis 2 on the dataset
z-axis-name=text
The text specified will become the name of the axis 0
title=path-into-nexus-file or text
If the value contains a / then it is interpreted as a path into the NeXus file, the value of which will be stored as workspace title. Else the text value will be stored as the title name directly.
sample=path-into-nexus-file or text
If the value contains a / then it is interpreted as a path into the NeXus file, the value of which will be stored as workspace sample. Else the text value will be stored as the sample name directly.

Please note that the dimensions on the MDHistoWorkspace are inverted when compared with the ones in the NeXus file. This is a fix which allows to efficiently transfer the NeXus data in C storage order into the MDHistoWorkspace which has fortran storage order.

Usage

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 AMOR Nexus file from SINQ/PSI:

import os
dictionary_path = os.path.join(config["instrumentDefinition.directory"], "nexusdictionaries")
wsOut = LoadFlexiNexus(Filename='amor2013n000366.hdf',
    Dictionary=os.path.join(dictionary_path, 'amor.dic'))

num_dims = wsOut.getNumDims()
print "This has loaded a MD Workspace with %i dimensions" % num_dims
print "Name   Bins   Min     Max"
for dim_index in range(num_dims):
    dim = wsOut.getDimension(dim_index)
    print "%s      %i    %.2f  %.2f" % (dim.getName(),
         dim.getNBins(), dim.getMinimum(), dim.getMaximum())

Output:

This has loaded a MD Workspace with 3 dimensions
Name   Bins   Min     Max
z      360    32471.45  194590.44
y      256    -95.00  94.26
x      128    -86.00  84.66

Categories: Algorithms | DataHandling\Nexus

Source

C++ source: LoadFlexiNexus.cpp

C++ header: LoadFlexiNexus.h