Fix exported workspaces in ALC

[Raquel Alvarez Banos]

Reported by James Lord and Jamie Peck:

In the exported Baseline workspace, there are three histograms corresponding to the three histograms created after a normal fit ("Data", "Calc" and "Diff", called "Data", "Baseline" and "Corrected" in this interface). The "Data" histogram has its original errors (OK), the "Baseline" histogram seems to have HUGE error bars (Bad) and the "Corrected" data has errors=0 (Bad). The same happens in the PeakFitting step when exporting fitting results.

This is caused by two different issues:

1. When exporting fitting results, the interface does not use the output workspace created by the Fit algorithm. Instead, it is doing the following:

• It creates a Fit algorithm and stores "Data", "Diff" and the fitted function in separate member variables.
• When exporting, it takes both "Data" and "Diff", and populates the "Calc" histogram by creating a new "Fit" algorithm with 0 iterations (which takes the previously fitted function). This is causing the "Baseline" (or equivalently "Calc") data to have huge errors. The interface SHOULD export the three spectra resulting from the first "Fit" algorithm.

This is a bug in the ALC interface and will be solved here.

2. The fit algorithm does not seem to compute errors for the "Diff" data, and therefore it causes the "Corrected" data in the interface to have zero errors.

This is related to the Fit algorithm and is not going to be solved here, I will create a new ticket for it.

[Raquel Alvarez Banos]

Re #11711 Keep all the fitting info in m_data

Changeset: 6dcb30531620aa0aa19fe7f23336493b9a274d87

[Raquel Alvarez Banos]

Re #11711 Fix unit test

Changeset: f800b2b8b11978d877694a6fed7d5607da6d9ded

[Raquel Alvarez Banos]

Re #11711 Store fitting results in m_data in the PeakFitting step

Changeset: 5de8e0d4a1fd9e064bbff490bb14afbe570ae7a7

[Raquel Alvarez Banos]

Re #11711 Fix crash when data has not been set

Changeset: d72bb0e1288bccd5bce21031c6782d6dd47f7f7e

[Raquel Alvarez Banos]

Re #11711 Recover original errors

Changeset: 85cae08f395877a5cf7be7e7d79ac9bcac7b9804

[Raquel Alvarez Banos]

Re #11711 Minor updates in unit tests

Changeset: 1cf34ea304e30f8bd4aae81ea75dd18de65431d7

[Raquel Alvarez]

This is being verified as ​pull request #725.

[Dan Nixon]

Merge pull request #725 from mantidproject/11711_Fix_exported_workspaces

Fix exported workspaces in ALC

Full changeset: ​18e57bd1d35ca14f999058696beb257b6f5b73fd

[Stuart Campbell]

This ticket has been transferred to github issue ​12549