problem with `viridis` on Ubuntu 20.04

On 30 April 2020 at 01:24, Samuele Carcagno wrote:
| I've hit a bug on Ubuntu 20.04. The issue occurred both with the R
| version that shipped with Ubuntu last week, and it is occurring now with
| the CRAN packages from one of the mirros (deb
| http://cran.mirror.garr.it/mirrors/CRAN/bin/linux/ubuntu/
| focal-cran40/). The issue occurs whether I use the deb package for
| viridis in the Ubuntu repos, or I install it with `install.packages()` in R.
|
| The issue is that when I call a function from the 'viridis' package
| (e.g. running the first example in the `viridis` vignette:
| https://cran.r-project.org/web/packages/viridis/vignettes/intro-to-viridis.html)
| R gets stuck indefinitely; the system monitor shows the R process using
| CPU resources but nothing happens at the terminal and I'm also unable to
| stop the function with Ctrl-C.
|
| I did a little digging and simply calling the function `viridis` from
| the `viridisLite` package causes the same problem, execution gets stuck
| at the line:
|
|      cols <- fn_cols(seq(begin, end, length.out = n)) / 255
|
| which is line 177 here:
| https://github.com/sjmgarnier/viridisLite/blob/master/R/viridis.R#L177
|
| I'm dual booting Debian Buster on the same machine and no such issue
| occurs with R 4.0.0 and the same versions of the `viridis` and
| `viridisLite` packages. Also no such issue occurs on Windows 10 or on a
| Mac both with R 4.0.0 and the latest versions of `viridis` and
| `viridisLite`.
|
| I was not sure where should I report the bug, so I thought of asking for
| advice here first.

Can we make it reproducible, please?  Can you provide a minimal script with
values for begin, end, n, ... etc pp or a concrete call?

I got lost in your description above between what version of R from where you
ran with which package or function.

Keep. It. Simple. And. Concise.

And reproducible.

For what it is worth, it _works for me with R 4.0.0 on Ubuntu 19.10_ with the
binary .deb from my PPA (as blogged about, but should be identical to what
Michael built and ships via CRAN).  Log of a fresh Emacs session below. I
double Ubuntu 20.04 is different but "one never knows".

Thank you!

Dirk

Log below

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    -- Peter Dalgaard (about an apparent non-bug report in his former R-announce message)
       R-help (December 2009)

R> setwd('/home/edd/')
R>
R> library(viridisLite)
R> example(viridis)

viridsR> library(ggplot2)

viridsR> library(hexbin)

viridsR> dat <- data.frame(x = rnorm(10000), y = rnorm(10000))

viridsR> ggplot(dat, aes(x = x, y = y)) +
virids+   geom_hex() + coord_fixed() +
virids+   scale_fill_gradientn(colours = viridis(256, option = "D"))
Hit <Return> to see next plot:

viridsR> # using code from RColorBrewer to demo the palette
viridsR> n = 200

viridsR> image(
virids+   1:n, 1, as.matrix(1:n),
virids+   col = viridis(n, option = "D"),
virids+   xlab = "viridis n", ylab = "", xaxt = "n", yaxt = "n", bty = "n"
virids+ )
Hit <Return> to see next plot:
R>