Example of colorise not working

[tamas-ferenci]

Here is a minimal reproducible example:

library(imager)
im <- load.example("coins")
colorise(im,~ x < 50,"blue") %>% plot

This results in Error in if (spectrum(px) != 1) { : argument is of length zero.

[ShotaOchi]

The example works on my machine. Can you show the result of sessionInfo()?

[tamas-ferenci]

Sure, thanks!

sessionInfo()
#> R version 4.0.4 (2021-02-15)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 10 x64 (build 19042)
#> 
#> Matrix products: default
#> 
#> locale:
#> [1] LC_COLLATE=Hungarian_Hungary.1250  LC_CTYPE=Hungarian_Hungary.1250   
#> [3] LC_MONETARY=Hungarian_Hungary.1250 LC_NUMERIC=C                      
#> [5] LC_TIME=Hungarian_Hungary.1250    
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 

[ShotaOchi]

The example works on my R 4.0.4 for Windows. What is the version of imager? And can you show the result of the following code?

library(imager)
im <- load.example("coins")
imeval(im, ~ x < 50) %>% print

[tamas-ferenci]

The version is imager 0.42.3 2020-05-11 [1] CRAN (R 4.0.3). Your code returns:

> im <- load.example("coins")
> imeval(im, ~ x < 50) %>% print
[1] NA

My naive debugging suggests that the problem is here: eval.form(args[[1]]) with eval.form being function(fo) parse(text = as.character(fo)[2]) %>% eval(envir = newenv). With this call the value of args[[1]] is ~x < 50, thus as.character(fo) is "~x < 50" which has no second component, thus it'll be NA, the eval of which is also NA.

[ShotaOchi]

It should be ok because args[[1]] is a formula. Consider the following example.

a <- ~ x < 50
as.character(a)

[1] "~" "x < 50"

as.character(a)[2]

[1] "x < 50"

[ShotaOchi]

I think eval function doesn't evaluate the formula as we expect for some reason. It seems that eval function finds the variables needed to evaluate the formula but they are not what we expect because eval function doesn't return an error. What is the result of imeval if you use basenev() as env?

library(imager)
im <- load.example("coins")
imeval(im, ~ x < 50, env = baseenv()) %>% print

[tamas-ferenci]

Wow, that's really strange. The problem is actually quite simple: as.character(~ x < 50) results in "~x < 50" at my computer.

I have absolutely no idea how is it possible, but I think you can close the issue now, because it has quite clearly nothing to do with imager. Thank you very much for the help in debugging!