Fix tidy.prcomp labels for loadings and scores matrices

[tavareshugo]

Hi,

I think there was a bug in tidy.prcomp() related to this commit, which moved code from using dplyr::gather() to dplyr::pivot_longer(). These two functions sort the output tibble in different ways, and so the labels being added with rep() were wrong when using tidy(x, matrix = "scores") and tidy(x, matrix = "loadings").

Here's an example (using broom v0.7.0):

library(magrittr)
set.seed(1)
m <- matrix(rnorm(8), ncol = 4)
rownames(m) <- paste0("row", 1:nrow(m))
colnames(m) <- paste0("col", 1:ncol(m))

x <- prcomp(m)

broom::tidy(x, "scores") %>% dplyr::arrange(PC)

Results in

# A tibble: 4 x 3
  row      PC     value
  <chr> <dbl>     <dbl>
1 row1      1 -1.41e+ 0
2 row1      1  1.41e+ 0
3 row2      2  0.      
4 row2      2  2.08e-17

The result we want is rather:

  row      PC     value
  <chr> <dbl>     <dbl>
1 row1      1 -1.41e+ 0
2 row2      1  1.41e+ 0
3 row1      2  0.      
4 row2      2  2.08e-17

I guess I could have just changed rep() to use each = ncomp rather than times = ncomp.
However, I think my fix is perhaps a bit simpler to read and more robust to future changes in how pivot_longer() sorts output. I took advantage of tibble::as_tibble() ability to add rownames as columns, and this works even if rownames(x) is NULL.

I hope the PR is helpful. (And thanks for the amazing package!)

[tavareshugo]

For consistency of returning integer when there are no rownames in the matrices, this could be added in.

[simonpcouch]

Thanks for pointing this out @tavareshugo!

Should I consider this PR ready to review? How should I interpret your review comments/suggestions?

[tavareshugo]

Hi @simonpcouch, thanks for having a look at this. I've committed my previous suggestions (i.e. for consistency with previous versions it returns labels as integer if rownames of those matrices are missing). I've also made a new commit adding my details to the contributors and a note to NEWS.md. So, I would say that this is ready for review now, thanks.

[simonpcouch]

Thanks for your patience with this, @tavareshugo. This code looks great to me, so I'll go ahead and resolve conflicts and merge! Much appreciated.

[tavareshugo]

thanks a lot @simonpcouch, I'm glad I could help a little bit with the package

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