Legend drops factor level named “recursive” in scale_*_manual()

[SbastianGarzon]

---

Hello, I found a (funny) problem when using the name "recursive" as a factor level in manual aesthetics. I was able to reproduce this problem using versions 4.0.1.9000 and 3.5.2.

library(ggplot2)

df <- data.frame(
  x = 1:3,
  y = 1:3,
  type = factor(c("none", "direct", "recursive"))
)

ggplot(df, aes(x, y, fill = type)) +
  geom_tile() +
  scale_fill_manual(
    values = c(
      "none" = "white",
      "direct" = "blue",
      "recursive" = "green"
    )
  )

As you can see, the legend should show all levels, including "recursive", but the legend drops the "recursive" category. If I rename "recursive" to any other word (e.g., even "Recursive" with a capital letter), the legend works again.

library(ggplot2)

df <- data.frame(
  x = 1:3,
  y = 1:3,
  type = factor(c("none", "direct", "Recursive"))
)

ggplot(df, aes(x, y, fill = type)) +
  geom_tile() +
  scale_fill_manual(
    values = c(
      "none" = "white",
      "direct" = "blue",
      "Recursive" = "green"
    )
  )

So, not a big problem (easy solution: change the name), but it makes me wonder if there are other "forbidden" words, and why this is happening. It took me a while to figure out why this was happening. I'm not including other examples with other aesthetics (e.g., scale_color_manual), but I was able to reproduce the same problem for different plots (geom_point, geom_tile...).

[teunbrand]

Thanks for the report! I can reproduce this from my end. This is unexpected, I should figure out why this occurs.

[teunbrand]

Ah, it turns out recursive is an actual argument to the c() function, so that is dropped from the vector. You can use setNames(c("white", "blue", "green"), c("none", "direct", "recursive")) instead. AFAIK there are no 'forbidden' words in ggplot2, but if you try to use use.names as a name, you may run into the same problem. In any case, I don't think ggplot2 carries the blame here.

[SbastianGarzon]

Oh! That makes sense. I did not think about the c() function. Thanks!