Reorder by X-axis

[Owen Arnold]

This relates to an issue reported by the user, where they have loaded ascii data in which the x-values are descending. It proves impossible to work with some features of mantid such as plotting if you do this.

The fix is simply to ensure that the x-axis is ordered smallest to largest, and that the y and e data also follow this ordering.

Using the data files attached and the following script, you can replicate this problem. Not that the plots generated do not graph the data properly as it is not ordered as expected.

# Load the text data.  Note, the erors bars are 0.0 due to the way they were processed earlier. 
Load(Filename=DataDir+'polref8481.dat',OutputWorkspace='r8481',Unit='MomentumTransfer')
Load(Filename=DataDir+'polref8483.dat',OutputWorkspace='r8483',Unit='MomentumTransfer')

# Display the data to see what we're starting with 
plotSpectrum([mtd['r8481'],mtd['r8483']],0)
# Notice that the default scaling is broken when the data has 

Rebin(InputWorkspace='r8481',OutputWorkspace='r8481',Params='0.009,-0.04,0.034',PreserveEvents='0')
Rebin(InputWorkspace='r8483',OutputWorkspace='r8483',Params='0.027,-0.04,0.150',PreserveEvents='0')

[Owen Arnold]

refs #7791. New algorithm and tests.

New algorithm SortXAxis is part of Transform/Axes. Unit tests show this algorithm working.

Changeset: 1480afa0e672ce3b9f7ce6a7f98a2af16f24b7dd

[Owen Arnold]

Tester: Follow the script, but run the algorithms

r8481=SortXAxis(InputWorkspace=r8481)
r8483=SortXAxis(InputWorkspace=r8483) 

directly after the load steps. You should then see the plots generated properly. You may also plot the ascii data directly in excel (for example) to compare against.

[Jay Rainey]

It appears you forgot to do git finish as your branch is not on github.

[Jay Rainey]

Merge remote-tracking branch 'origin/feature/7791_sort_x_axis'

[Jay Rainey]

Testing

• Tested on Ubuntu 12.04.
• X-axis is now ordered smallest to largest allowing graphs to be produced.
• All unit tests pass.

Code review

• Well written and documented code, especially the unit test.

[Stuart Campbell]

This ticket has been transferred to github issue ​8636