exportData

Overview

Once data have been reduced, they are available as mantid workspaces and are also automatically saved as .nxs files along with a detailed reductionRecord that captures all parameters used in reduction. In addition, it’s usually necessary to export data in appropriate formats for subsequent analysis, exportData enables this.

By default, exportData will output all available reduced data workspaces in three pre-defined formats:

• gsa GSAS and GSAS2 format output. Different pixel groups are stored as separate “banks” in the output file

• xye TOPAS and FULPROF format output. Different pixel groups are stored as separate output files

• csv PARIALLY IMPLEMENTED: currently the output is called .csv but is actually tab delineated. Nevertheless, this provides a simple ascii format with the reduced data as a function of d-spacing

As noted in the description of reduce, multiple reductions of the same run are supported by adding a suffix with a timestamp to the end of a mantid workspace name. However, by default, only the most recent workspace will be exported and the timestamp will not be used in the exported filename. It is possible to override this if necessary (see below) if refinement of different reduction treatements is useful (e.g. to test different attenuation corrections)

Finally, it is intended to automatically link output files to corresponding templates and or instprm files (in the case of GSAS). This work is on going, however, already exportData will automatically create a “dummy” gsas instprm file by default. This file is given the same file name (but a different extension) to the exported GSAS/GSAS2 data and it will be automatically used when loading the data (.gsa file) into GSAS2.

Warning

At present the autocreated GSAS2 .instprm file should be viewed as an approximate starting point. It is not a fully calibrated file! Work is ongoing to figure out how to propagate existing, manually calibrated instPrm files however, since these are needed for each state and for each pixel group within a state, some kind of automated solution is desirable. This isn’t trivial to realise though…

Export locations

By default, data are exported to the IPTS/shared directory according to the reduced run number and a subdirectory in there called /SNAPRed/export. Within this subdirectory separate folders will be created for each requested export format and, within these, separate folders for each pixel grouping scheme used during reduction.

e.g.

/SNS/SNAP/IPTS-34952/shared/SNAPRed/export/gsa/column/

It is sometime useful/necessary to export data to an IPTS that different from what the data were measured under. In this case, the parameter iptsOverride can be used (see below)

Optional arguments

prefix

Data reduced by SNAPRed will have a workspace with names that begin with the prefix reduced_dsp. By default, all workspaces with this prefix will be processed by exportData. However it is possible to specify a different prefix.

For example, if data have been downsampled, they will be stored in workspaces with a prefix resampled_dsp. Or, if data have been converted to units of momentum transfer, they will have the prefix reduced_qsp.

As long as workspaces follow the naming convention

{prefix}_{pixelgroup}_{runNumber}_{timestamp}

exportData should be able to process these.

exportFormats

The desired export formats can be specified using this parameter. Its value is in the form of a list of string, each supported string is a 3 character as described in the overview. The default value of this parameter is [‘gsa’,’xye’,’csv’] and all three formats will be created.

If a different format needs to be supported, just let the SNAP Team know.

latestOnly

Defaulting to True this ensures that only the latest reduced workspace is exported and that its timestamp is excluded from the exported filename. If, instead, this is set False all existing reductions of a given run are exported and their filenames will include their timestamps.

gsasInstPrm

Defaults to True. This will export a dummy instPrm to the gsas export folder with the same name as the exported data.

fileTag

This should be a string which, if specified, will be added to the name of the output reduced data file. e.g.

wrap.exportData(fileTag='banana')

will create output data with filenames that end _banana.