René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"DOC: Really add an arrow tutorial","articleBody":"In #11219 and #11223 @dstansby headed out to provide an arrow tutorial. Since the scope of this was rather limited, it ended up as an example [examples/shapes_and_collections/arrow_guide.py](https://matplotlib.org/devdocs/gallery/shapes_and_collections/arrow_guide.htm) - which is great. \r\n\r\nHowever as mentionned in this PR #11223 there are a lot of other things to consider about arrows. In the end it would be good to have something like a complete \"Arrow tutorial\". I'm collecting the comments in this thread for them not to get lost, once someone has more time to write this up.\r\n\r\nThere currently are already the [annotation_demo](https://matplotlib.org/gallery/text_labels_and_annotations/annotation_demo.html) example and the [annotations](https://matplotlib.org/users/annotations.html) tutorial. So I wonder in how far they are overlapping or not. Independent of that, there should be links in between them.\r\n\r\nIn addition, the following things should be considered when writing :\r\n\r\n* what is the relation between `ax.arrow`, `ax.annotate`, `ax.quiver`, `mpatches.FancyArrowPatch`? \r\n* Any user looking at the `patches` doc would directly ask: \"What is the difference between `Arrow`, `FancyArrow`, `FancyArrowPatch` and `YAArrow`?\" A tutorial might want to answer this.\r\n* The problem when drawing arrows is mostly to understand all the different parameters. Common questions could be \r\n  * How to make the head larger?\r\n  * What are the units of `head_length`, `head_width`, `tail_width`, `mutation_scale`,  etc.?\r\n  * Why is my arrow shorter than the distance between the two points I specified?\r\n  * Why can't I use an `FancyArrowPatch` in a collection? What's the alternative? (should be checked when deprecating other arrows)\r\n  *  How do I draw an arrow with a dotted tail?\r\n  * When should I use a `ConnectionPatch` instead of a `FancyArrowPatch`?\r\n* Is the [arrow_demo](https://matplotlib.org/3.0.0/gallery/text_labels_and_annotations/arrow_demo.html) useful? Can it be replaced by something simpler? Definitely explain `plt.arrow`'s `length_includes_head` and possibly `head_starts_at_zero` -\u003e #12768\r\n* Apperently it's not possible to get an arrow with a bolder connection path in the middle and two arrow heads on both sides? ([This SO question](https://stackoverflow.com/questions/57642971/how-to-create-filled-in-default-style-double-ended-arrows-with-matplotlib?noredirect=1#57642971)) Need to check.","author":{"url":"https://github.com/ImportanceOfBeingErnest","@type":"Person","name":"ImportanceOfBeingErnest"},"datePublished":"2018-05-31T11:18:10.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/11350/matplotlib/issues/11350"}