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# SaveNexusProcessed v1¶

## Summary¶

The SaveNexusProcessed algorithm will write the given Mantid workspace to a Nexus file. SaveNexusProcessed may be invoked by SaveNexus.

## Properties¶

Name

Direction

Type

Default

Description

InputWorkspace

Input

Workspace

Mandatory

Name of the workspace to be saved

Filename

Input

string

Mandatory

The name of the Nexus file to write, as a full or relative path. Allowed extensions: [‘.nxs’, ‘.nx5’, ‘.xml’]

Title

Input

string

A title to describe the saved workspace

WorkspaceIndexMin

Input

number

0

Index number of first spectrum to write, only for single period data.

WorkspaceIndexMax

Input

number

Optional

Index of last spectrum to write, only for single period data.

WorkspaceIndexList

Input

int list

List of spectrum numbers to read, only for single period data.

Append

Input

boolean

False

Determines whether .nxs file needs to be over written or appended

PreserveEvents

Input

boolean

True

For EventWorkspaces, preserve the events when saving (default). If false, will save the 2D histogram version of the workspace with the current binning parameters.

CompressNexus

Input

boolean

False

For EventWorkspaces, compress the Nexus data field (default False). This will make smaller files but takes much longer.

## Description¶

The algorithm SaveNexusProcessed will write a Nexus data file from the named workspace. This can later be loaded using LoadNexusProcessed v2.

The file name can be an absolute or relative path and should have the extension .nxs, .nx5 or .xml. Warning - using XML format can be extremely slow for large data sets and generate very large files. Both the extensions nxs and nx5 will generate HDF5 files.

The optional parameters can be used to control which spectra are saved into the file. If WorkspaceIndexMin and WorkspaceIndexMax are given, then only that range to data will be loaded.

A Mantid Nexus file may contain several workspace entries each labelled with an integer starting at 1. If the file already contains n workspaces, the new one will be labelled n+1.

### Time series data¶

TimeSeriesProperty data within the workspace will be saved as NXlog sections in the Nexus file. Only floating point logs are stored and loaded at present.

### EventWorkspaces¶

This algorithm will save EventWorkspaces with full event data, unless you uncheck PreserveEvents, in which case the histogram version of the workspace is saved.

Optionally, you can check CompressNexus, which will compress the event data. Warning! This can be very slow, and only gives approx. 40% compression because event data is typically denser than histogram data. CompressNexus is off by default.

## Usage¶

Example - a basic example using SaveNexusProcessed.

import os

ws = CreateSampleWorkspace()
file_name = "myworkspace.nxs"
path = os.path.join(os.path.expanduser("~"), file_name)
SaveNexusProcessed(ws, path)

print(os.path.isfile(path))


Output:

True


Example - an example using SaveNexusProcessed with additional options.

import os

ws = CreateSampleWorkspace()
file_name = "myworkspace.nxs"
path = os.path.join(os.path.expanduser("~"), file_name)
SaveNexusProcessed(ws, path, Title="MyWorkspace", WorkspaceIndexMin=0, WorkspaceIndexMax=9)

print(os.path.isfile(path))

print("Saved workspace has {} spectra".format(ws.getNumberHistograms()))


Output:

True
Saved workspace has 10 spectra


Example - an example using SaveNexusProcessed to save an Event workspace.

import os

ws = CreateSampleWorkspace("Event")
file_name = "myworkspace.nxs"
path = os.path.join(os.path.expanduser("~"), file_name)
SaveNexusProcessed(ws, path, CompressNexus=True, PreserveEvents=True)

print(os.path.isfile(path))

print("Saved workspace has {} spectra".format(ws.getNumberHistograms()))


Output:

True
Saved workspace has 200 spectra


Categories: AlgorithmIndex | DataHandling\Nexus