Plotting entitysets

[floscha]

This PR adds a plot() method to the EntitySet class as described in #381, as well as a suite of relevant unit tests.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #382 into master will decrease coverage by 0.08%.
The diff coverage is 84.74%.

@@            Coverage Diff             @@
##           master     #382      +/-   ##
==========================================
- Coverage   95.85%   95.77%   -0.09%     
==========================================
  Files          89       90       +1     
  Lines        7798     7857      +59     
==========================================
+ Hits         7475     7525      +50     
- Misses        323      332       +9

Impacted Files	Coverage Δ
...eaturetools/tests/entityset_tests/test_plotting.py	100% <100%> (ø)
featuretools/entityset/entityset.py	94.2% <70%> (-1.55%)	⬇️

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[kmax12]

thank you for the contribution - let us know when it's ready for review.

note: don't worry about the failing codecov checks. those seem to be errors. if you update from master, it may fix

[floscha]

Thanks for the hint. I was already having a hard time figuring out how my changes could've increased the number of misses... Other than that, I'd say the PR is ready for review now

[kmax12]

great. someone on our side will review soon.

[kmax12]

Looking good. Just my comments and couple more things below related to docs

1. Can you add this to api_reference.rst?
2. Can you add this using_entitysets.rst as a note somewhere towards the top?

.. note ::

  You can visualize your entity set structure by using the `EntitySet.plot()` method.

If it's a bit confusing working with docs, let me know and I can help.

Thanks for the contribution!

[kmax12]

can we make this an optional requirement?

my recommended approach would be to import inside of plot some like this

try:
    import graphviz
except ImportError:
    raise ImportError('Please install graphviz to install use plotting functionality')

[floscha]

Fair enough. It's now solved with a779771

[kmax12]

i believe this edge is going in wrong direction. the arrow should point from the child to the parent.

for example in the attached image the orders entity should points to the customers, rather than the other way around

[floscha]

You're right regarding the direction. Also, this page suggests that there's a dedicated "one-to-many"-relationship arrowhead, which I also added with 1216fb4 and made all lines orthogonal. Furthermore, if the key is the same for both related entities, the key is now only displayed once.

The result now looks like this:

I'm not 100% satisfied with the aesthetics but I guess that'll have to do for now.

[floscha]

Thanks for your feedback @kmax12. I've extended the docs with 11ce114 (I hope I've done that part right) and incorporated your comments (see above).

[kmax12]

@floscha looks like there are a few linting errors being caught in CI. they are

featuretools/entityset/entityset.py:8:1: F401 'graphviz' imported but unused
featuretools/entityset/entityset.py:1111:13: F811 redefinition of unused 'graphviz' from line 8
featuretools/entityset/entityset.py:1136:55: E231 missing whitespace after ':'

you should be able to reproduce locally by running make lint.

[floscha]

My bad. They're fixed now

[kmax12]

This looks great. I just made a some changes to the docs and reverted the arrow back to what you had before.

Merging now.