add option to locate axis labels at positive ends

[corybrunson]

As suggested here, this would communicate important information to the reader more efficiently than reading the tick labels. This should probably be the default option, with other options for the opposite (placing labels at negative ends) and for the current attempt to locate them farther from the action.

I'm having trouble with {reprex}, but the following code produces an example of the current behavior:

library(ordr)
ordinate(USJudgeRatings, princomp) |> 
  ggbiplot() +
  geom_rows_point(elements = "score") +
  geom_cols_axis(aes(label = name)) +
  xlim(c(-5, 8)) + ylim(c(NA, 3.5))

[corybrunson]

@jtr13 per your suggestion here, the end-labels branch (of {gggda}) introduces the label_placement parameter and defaults to the new option "positive"; install from that branch and see the documentation for details. I've reproduced your example below, also accounting for some changes to the geom_axis() parameters (from label_size to size and from label_color to label.color). Does this suit you? Would you suggest any additional changes, e.g. "increasing" and "decreasing" rather than "positive" and "negative"?

library(Lock5withR)
library(ordr)
#> Loading required package: ggplot2
pca_ordr <- ordinate(Cereal, cols = 3:10,
                     model = ~ prcomp(., scale. = TRUE))

ggbiplot(pca_ordr) +
  geom_rows_point(size = 1, color = "cornflowerblue") +
  geom_rows_text_repel(aes(label = Name), size = 2, color = "cornflowerblue") +
  geom_cols_vector(color = "red", vector_labels = FALSE) +
  geom_cols_axis(aes(label = name), size = 2.5, label.color = "red", num = 10) +
  stat_rows_projection(subset = 23, ref_subset = c(2, 4, 6), color = "blue", linetype = "dashed") +
  xlim(c(-5, 5)) +
  theme_minimal()
#> `subset` will be applied after data are restricted to active elements.
#> This message is displayed once per session.

^{Created on 2025-08-06 with reprex v2.1.1}

Thanks for the great suggestion!

[corybrunson]

NB: Tests are needed for edge cases (vertical axes).