Create new axes with specified projection without using gca(...)

[tkphd]

Closes #369.

[codecov]

Codecov Report

Merging #370 (6d6fc9e) into develop (77f25eb) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #370      +/-   ##
===========================================
- Coverage    89.93%   89.92%   -0.01%     
===========================================
  Files           44       44              
  Lines         4370     4368       -2     
===========================================
- Hits          3930     3928       -2     
  Misses         440      440              

Impacted Files	Coverage Δ
pycalphad/plot/eqplot.py	68.88% <100.00%> (-0.68%)	⬇️

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[richardotis]

Thanks Trevor! My only question was to figure out if matplotlib 3.3 (our current required minimum version) was recent enough for subplot_kw, but it looks like the feature is at least a few years old.

[richardotis]

Can you also update the TernaryExamples notebook in the examples folder with the same fix?

[tkphd]

Happy to help @richardotis! Enjoying the new (to me) functionality.
Quaternary dataviz next?

[richardotis]

@tkphd General isopleth calculation is on the roadmap and probably the biggest feature blocking "pycalphad 1.0". @bocklund has been thinking hard about general phase diagram mapping, including isopleth calculation. A recent paper from Sundman et al describes the challenges with the general case: https://doi.org/10.1016/j.calphad.2021.102330

In short, there's a lot of state to track for multicomponent isopleths, and it's easy to accidentally compute a metastable diagram. I can't promise a timeline except to say that this year's new energy minimization module (shipped in 0.9) was definitely a prerequisite to further progress, and I think we're in good position to ship "something" related to mapping in 2022. We are open to collaborations in this direction,