some improvements to the documentation

Author: rasbt

docs/mkdocs.yml

@@ -108,6 +108,7 @@ nav:
   - plotting:
     - user_guide/plotting/category_scatter.md
     - user_guide/plotting/checkerboard_plot.md
+    - user_guide/plotting/plot_pca_correlation_graph.md
     - user_guide/plotting/ecdf.md
     - user_guide/plotting/enrichment_plot.md
     - user_guide/plotting/plot_confusion_matrix.md

docs/sources/USER_GUIDE_INDEX.md

@@ -83,6 +83,7 @@
 - [ecdf](user_guide/plotting/ecdf.md)
 - [enrichment_plot](user_guide/plotting/enrichment_plot.md)
 - [plot_confusion_matrix](user_guide/plotting/plot_confusion_matrix.md)
+- [plot_pca_correlation_graph](user_guide/plotting/plot_pca_correlation_graph.md)
 - [plot_decision_regions](user_guide/plotting/plot_decision_regions.md)
 - [plot_learning_curves](user_guide/plotting/plot_learning_curves.md)
 - [plot_linear_regression](user_guide/plotting/plot_linear_regression.md)