Allow marker style to be specified in Validation Curve

[lwgray]

3. Summarize your PR (HINT: See CHECKLIST/TEMPLATE below!) -->

This PR addresses StackOverflow question regarding how to change the marker of Validation Curve. https://stackoverflow.com/questions/67267401/how-to-change-the-marker-in-yellowbrick-plots

I have made the following changes:

1. Added marker argument to both ValidationCurve and quickmethod

Sample Code and Plot (Original [Top], New [Bottom])

import numpy as np

from yellowbrick.datasets import load_energy
from yellowbrick.model_selection import ValidationCurve

from sklearn.tree import DecisionTreeRegressor

# Load a regression dataset
X, y = load_energy()

viz = ValidationCurve(
    DecisionTreeRegressor(), param_name="max_depth",
    param_range=np.arange(1, 11), cv=10, scoring="r2",
    markers="-v"
)

# Fit and show the visualizer
viz.fit(X, y)
viz.show()

TODOs and questions

Still to do:

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Questions for the @DistrictDataLabs/team-oz-maintainers:

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CHECKLIST

• [x] Is the commit message formatted correctly?
• [ ] Have you noted the new functionality/bugfix in the release notes of the next release?

• [x] Included a sample plot to visually illustrate your changes?
• [x] Do all of your functions and methods have docstrings?
• [ ] Have you added/updated unit tests where appropriate?
• [x] Have you updated the baseline images if necessary?
• [x] Have you run the unit tests using pytest?
• [x] Is your code style correct (are you using PEP8, pyflakes)?
• [ ] Have you documented your new feature/functionality in the docs?

• [ ] Have you built the docs using make html?

[codecov[bot]]

Codecov Report

Merging #1258 (f1f30c4) into develop (5d54821) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #1258   +/-   ##
========================================
  Coverage    90.75%   90.75%           
========================================
  Files           93       93           
  Lines         5300     5301    +1     
========================================
+ Hits          4810     4811    +1     
  Misses         490      490           

Impacted Files	Coverage Δ
yellowbrick/model_selection/validation_curve.py	98.14% <100.00%> (+0.03%)	:arrow_up:

:mega: Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[lwgray]

@rebeccabilbro where are you seeing the annotation error? During building the docs????

[rebeccabilbro]

@rebeccabilbro where are you seeing the annotation error? During building the docs????

@lwgray look in your PR diff in the “files changed” view, all the way at the bottom.

[lwgray]

@rebeccabilbro I am unsure how to resolve the umap annotation check. Any suggestions?

[rebeccabilbro]

@lwgray ah ok - have you already tried updating the umap version in docs/requirements.txt as suggested above?

[lwgray]

docs/requirements doesn't have umap

[rebeccabilbro]

docs/requirements doesn't have umap

That’s probably the problem :)

[lwgray]

@rebeccabilbro Adding umap to requirements doesn't resolve the issue....It is specific to this plot directive for umap quick-method as other umap Visualizer plot directives appear to run without issue

[rebeccabilbro]

FYI @lwgray this has been approved but left unmerged for over a month

[lwgray]

@rebeccabilbro I didn't merge because i couldn't resolve the annotation error you brought up. @bbengfort can you assist us?

[rebeccabilbro]

@lwgray Benjamin is on vacation. I'm going to merge this once the tests pass with @pdamodaran's updates. In the future, please merge your own PRs once you've received an approval.

[rebeccabilbro]

Unfortunately @lwgray it looks like you have a bit of new work to do to get all the image comparison checks to pass. Hopefully this won't take too much work on your part!