suppress "Each group consists of only one observation"

[andybeet]

• Allow user to suppress messages like " geom_line(): Each group consists of only one observation. Do you need to adjust the group aesthetic?"

While you can (sometimes) eliminate this message if you use groups=1 or convert variables from factor to numeric, in one case you can not; when geom_line is used in a facet plot and one of the facets has only one data point. This makes rmd's a little ugly

---

  # remove all but one row where cyl == 6 (mtcars)
ind <- which(mtcars$cyl == 6)
exclude <- head(ind,-1)
mtcars2 <- mtcars |> 
  dplyr::slice(-exclude)


ggplot2::ggplot(mtcars2,ggplot2::aes(x=mpg,y=wt)) +
  ggplot2::geom_point() + 
  ggplot2::geom_line() +
  ggplot2::facet_wrap(~cyl)
#> `geom_line()`: Each group consists of only one observation.
#> ℹ Do you need to adjust the group aesthetic?

^{Created on 2024-07-24 with reprex v2.1.0}

[teunbrand]

These messages are suppressable through the usual methods of suppressMessages() or chunk options like message=FALSE. I don't think they're more annoying than they are helpful.

[andybeet]

@teunbrand Unfortunately, the message is not suppressable using those methods.

Not sure how to demonstrate this with a reprex of a rendered rmarkdown, but if you were to copy the snippet into an rmarkdown yourself you will see. Here is a "combo" chunk:

```{r cars, message=FALSE}
  # remove all but one row where cyl == 6 (mtcars)
ind <- which(mtcars$cyl == 6)
exclude <- head(ind,-1)
mtcars2 <- mtcars |> 
  dplyr::slice(-exclude)


p <- ggplot2::ggplot(mtcars2,ggplot2::aes(x=mpg,y=wt)) +
  ggplot2::geom_point() + 
  ggplot2::geom_line() +
  ggplot2::facet_wrap(~cyl)

suppressMessages(p)

Still results in the message being displayed

[teunbrand]

The trick is to have the print()ing happen inside the context of a chunk. If you're just passing p the printing happens outside the chunk and hence the message handler doesn't apply. You should use suppressMessages(print(p)) instead.
Also using only one of message=FALSE in the chunk options or suppressMessages() would suffice.

[andybeet]

ok, This works. (message=F does not).

```{r cars}
  # remove all but one row where cyl == 6 (mtcars)
ind <- which(mtcars$cyl == 6)
exclude <- head(ind,-1)
mtcars2 <- mtcars |> 
  dplyr::slice(-exclude)


p <- ggplot2::ggplot(mtcars2,ggplot2::aes(x=mpg,y=wt)) +
  ggplot2::geom_point() + 
  ggplot2::geom_line() +
  ggplot2::facet_wrap(~cyl)

suppressMessages(print(p))

[teunbrand]

With message=FALSE you should still use print(p) rather than just p