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Polish ordered factors

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Hadley Wickham 2022-08-08 12:06:34 -05:00
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factors.qmd
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@ -414,7 +414,7 @@ Read the documentation to learn about `fct_lump_min()` and `fct_lump_prop()` whi
## Ordered factors
Before we go on, there's a special type of factor that needs to be mentioned briefly: ordered factors.
Ordered factors, created with `ordered()`, imply a strict ordering of levels such that the first level is "less than" the second level and so on.
Ordered factors, created with `ordered()`, imply a strict ordering and equal distance between levels: the first level is "less than" the second level by the same amount that the second level is "less than" the third level, and so on..
You can recognize them when printing because they use `<` between the factor levels:
```{r}
@ -422,9 +422,9 @@ ordered(c("a", "b", "c"))
```
In practice, `ordered()` factors behave very similarly to regular factors.
There are only two places where you might notice different behaviour:
There are only two places where you might notice different behavior:
- If you map an ordered factor to color or fill in ggplot2, it will default to `scale_color_viridis()`/`scale_fill_viridis()`, a color scale that implies a ranking.
- If you use an ordered function in a linear model, it will use "polygonal contrasts". These are midly useful, but you are unlikely to have heard of them unless you have a PhD in Statistics, and even then you probably don't routinely interpret them.
- If you use an ordered function in a linear model, it will use "polygonal contrasts". These are mildly useful, but you are unlikely to have heard of them unless you have a PhD in Statistics, and even then you probably don't routinely interpret them.
Given the arguable utility of these differences, we don't generally recommend using ordered factors.