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SaveISISReflectometryORSO v1

Summary

Saves ISIS processed reflectometry workspaces into the ASCII implementation of the ORSO data standard.

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	The workspace containing the reduced reflectivity data to save.
WriteResolution	Input	boolean	True	Whether to compute resolution values and write them as the fourth data column.
Filename	Input	string	Mandatory	File path to save the .ort file to. Allowed extensions: [‘.ort’]

Description

This algorithm saves the data and relevant metadata from a reduced ISIS Reflectometry workspace into the ASCII implementation of the ORSO data standard [1]. The orsopy library [2] is used to format and write out the .ort file. Currently this algorithm is unable to collect all of the mandatory information required by the ORSO standard so it produces a file that is not fully ORSO compliant. A comment is included at the top of the file to reflect this. This algorithm is only suitable for use with Reflectometry data collected at the ISIS Neutron and Muon facility.

The InputWorkspace passed to the algorithm should be a reduced Reflectometry workspace in units of momentum transfer (Q). The algorithm attempts to find metadata for the file header and the resolution (dQ/Q) from the instrument, workspace history and sample logs associated with the workspace. As a result, this algorithm may produce a file that is missing information if it is passed a workspace that wasn’t reduced via the ISIS Reflectometry Interface. See below for further information about where the metadata and resolution are searched for in the workspace.

This algorithm currently does not work correctly with workspace groups.

Data values

The saved .ort file contains at least three columns of data: the normal wavevector transfer (Qz), the reflectivity (R) and the error of the reflectivity. The data is converted to point data using algorithm ConvertToPointData v1 before being saved to file.

If parameter WriteResolution is set to True then the algorithm will also attempt to include a fourth column that calculates the resolution of the normal wavevector transfer as: \(resolution * Qz\). The resolution (dQ/Q) is looked up from the workspace history as follows:

• Find the last occurrence of Stitch1DMany v1 in the workspace history. If this can be found, then the absolute value of the stitch Params parameter is used for the resolution.

• Otherwise, find the last occurrence of ReflectometryReductionOneAuto v3. This algorithm makes a call to Rebin v1 and the absolute value of the middle rebin Params parameter is used as the resolution.

If a resolution value cannot be found from the workspace history then a warning is logged and the file is saved without this column included.

Header Metadata

Some of the metadata for the ORSO file header is retrieved directly from the input workspace, as described below:

Header value	Workspace location
instrument	The name of the instrument associated with the workspace.
start_date	The value of the run_start sample log.
proposalID	The value of either the rb_proposal or experiment_identifier sample log.
sample name	The workspace title (same as the value of the run_title sample log).
reduction timestamp	The execution time of the last occurrence of ReflectometryReductionOneAuto v3 in the workspace history.

Usage

Example - Save a workspace in ISIS reflectometry ORSO ASCII format

# import the os path libraries for directory functions
import os

ws = CreateSampleWorkspace(XUnit="MomentumTransfer")

# Create an absolute path by joining the proposed filename to a directory
# os.path.expanduser("~") used in this case returns the home directory of the current user
file = os.path.join(os.path.expanduser("~"), "ws")

# Add Sample Log entries
AddSampleLog(Workspace=ws, LogName='rb_proposal', LogText='1234', LogType='Number')

# Save the ORSO file
SaveISISReflectometryORSO(InputWorkspace=ws, Filename=file, WriteResolution=False)

# Open the file and read the first line
if os.path.exists(file + ".ort"):
  with open((file + ".ort"), 'r') as myFile:
    print(myFile.readline())

# # ORSO reflectivity data file | ... standard | YAML encoding | https://www.reflectometry.org/

References

[1]

ORSO file format specification: https://www.reflectometry.org/file_format/specification

[2]

orsopy Python library: https://orsopy.readthedocs.io/en/latest/

Categories: AlgorithmIndex | Reflectometry\ISIS

Source

Python: SaveISISReflectometryORSO.py