04-data-structures-part1 doesn't mention operations with matrices

[rgaiacs]

When you say matrices I think in linear algebra. Right after you teach me how I can create one matrix in R I will want to know how I can execute linear algebra operations in R, e.g. sum and multiplication. But

> A <- matrix(c(1,2,3,4), ncol=2, nrow=2)
> x <- matrix(c(1,2), ncol=1, nrow=2)
> A
     [,1] [,2]
[1,]    1    3
[2,]    2    4
> x
     [,1]
[1,]    1
[2,]    2
> A * x
Error in A * x : non-conformable arrays

I think this should go into one challenge.

[naupaka]

Good idea @rgaiacs. I added this issue to the milestone for the Bug BBQ and hopefully someone will open a PR to resolve it.

[tomwright01]

This content really doesn't fit in 04-data-structures. Matrix multiplication is covered in 09-vectorisation. I suggest we close this issue.

[jrnold]

Since operations of vectors are not discussed in 04-data-structures, I agree with @tomwright01 . However, why does the vectorisation lesson come so far after data structures? It seems like it should be the next lesson.

[gvdr]

Agreed on matrix operations. I would move the Matrix section above the data.frame, though, because data.frames are more general. What do you think?

[jrnold]

Though if someone is completely new the current order may work well. You can introduce data frames as a general case. Then matrices as something less general: a table in which everything has to be the same type. Under the hood they are implemented very differently, but to the user that may be the easiest way to initially understand the difference.

[naupaka]

It sounds like there is support for leaving it as is, so I'd like to close this issue unless anyone has strong objections? Currently, the content is covered in 09-vectorization, so the question as I understand it is about the proper placement of that content relative to content about data frames.

[tomwright01]

I don't think there is any problem moving 09-vectorisation. The question is where to?

Obviously after 04-data structures, but we don't want to push creating graphs back too far. I suggest after "subsetting data" but then swap "control flow" and "creating graphics".

The final order would then be:

1. Introduction to R and RStudio
2. Project management with RStudio
3. Seeking help
4. Data structures
5. Exploring Data Frames
6. Subsetting data
7. Vectorisation
8. Creating publication quality graphics
9. Control flow
10. Functions explained
11. Writing data
12. Split-apply-combine
13. Dataframe manipulation with dplyr
14. Dataframe manipulation with tidyr
15. Producing reports with knitr
16. Best practices for writing good code

Feel free to close this though. Otherwise I can probably make these changes this afternoon.

[gvdr]

Oh, no, sorry, my point was not to move 09. Was to move the paragraph about matrices that is already within 04 above data frames. I see no reason to have it after data frames in that chapter: it does not use any of the concepts introduced for data frames, but relies only on vectors... I still think chapter 04 may take advantage of a reflowing.

[naupaka]

Closing b/c of no activity and support for leaving order as-is.