Issue 1006 process space var

[rtimms]

Description

Extend processed_variable to work in the case when len(t_sol)=1 and also makes it so you no longer need to pass t to the call in the cases where the variable is constant (doesn't depend on t or y) or when len(solution.t)=1 (e.g. algebraic models)

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #1006 and #571

EDIT: Note that for variables discretised using finite elements (in y and z) the result returned by ProcessedVariable is transposed. This is consistent with other features, e.g. you can now do plt.pcolormesh(x,y,z) where z is some variable discretised with finite elements, whereas before you had to do plt.pcolormesh(x,y,np.transpose(z))

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[valentinsulzer]

Looks good to me!

[valentinsulzer]

is there no way around the duplication of all these lines?

[rtimms]

yep, have made a function to take the interpolant and inputs and returns the result of the correct shape

[valentinsulzer]

duplicated here