[Concept Exercise] Cheese Club

[colinleach]

This is the best I've so far come up with for functional-programming. Adapted from Julia, I added name_customer() to practice map2(), and removed the make-a-matrix task (in the light of my skeptical comments in that Concept!).

Testing is quite light: probably enough, but let me know if you disagree.

The Introduction covers so much ground in overview format that I took the unusual step of leaving lots of links in. I don't think students can grapple with a sprawling library like purrr without looking at the docs, so links make it easier for them.

Once we agree an introduction.md here I'll copy it back to #501. A very central concept, literally - it should finally join up the concepts into a single connected tree (though with functions still missing).

[depial]

LG2M!

I think testing is likely fine for the exercises.

I wish we could squeeze in some more functionality from the introduction. One thought for a task could be to ask for the differences between the ratings, as a sort of discrete derivative, to track customers' experiences between cheeses. This would encourage an accumulate(ratings, -)...

Nothing extravagant, just a thought.

[colinleach]

I wish we could squeeze in some more functionality from the introduction

Let's delay merging this while I think about it. Meanwhile, I'll copy the intro to the Concept, so we can merge that.

[depial]

If we stick with the current tasks, it seems like the section Reduce functions could be dropped from the Intro.

[colinleach]

it seems like the section Reduce functions could be dropped from the Intro

I'll certainly leave it in the Concept intro. For the exercise, I'd rather use it in a task than drop it (details still TBD).

[colinleach]

Using accumulate() proved harder than I thought. I cheated, and created a simple task with cummean() from dplyr.

The extra bit in introduction.md needs to be copied to the concept docs. I'll do that in this PR, if I can rebase without wrecking everything.

update: concept docs also changed.

[depial]

Using accumulate() proved harder than I thought. I cheated, and created a simple task with cummean() from dplyr.

We could probably give a bit more in the hints.md to help this along.

Some ways I could think of solving it:

accumulate(ratings, `+`) |> map2_dbl(1:length(ratings), `/`)

cumsum(ratings) |> map2_dbl(1:length(ratings), `/`)

accumulate(ratings, `+`) / 1:length(ratings)

cumsum(ratings) / 1:length(ratings)

The first two seem to be most in line with what we're aiming at in this concept, but I'm not sure if you feel there's a good way to hint towards any of these.

EDIT: To complement your current hint, I suppose I couldn't hurt just to include another like:

• This can be accomplished with an accumulate and a map2

Or something to that effect.

[colinleach]

I've added a few more lines to the hints. On the right track?

I think it can also be useful to post multiple approaches in our solution of this exercise, so they show up in Community Solutions.

[depial]

That seems good to me, the only other question that comes to mind is if we should explicitly mention map2_dbl or just leave it at map2. I'm ambivalent, so I'll let you decide what you think is best, and you can merge when you feel comfortable.

[colinleach]

The syllabus looks a lot nicer on the website not that it's all joined up into a connected tree.

I ran the solutions successfully, with a couple of approaches to task 5.