Can't select bands with descending index

[kadyb]

tif = system.file("tif/olinda_dem_utm25s.tif", package = "stars")
tif = c(tif, tif, tif, tif, tif)
x = read_stars(tif, proxy = TRUE, along = 3)
x[,,,1:3] # works
x[,,,3:1] # doesn't work

[edzer]

That indeed doesn't work. Would it be O.K. if it raises an error, or is this something that you need?

[kadyb]

So I have a bigger issue. If we can't use descending indices in stars.proxy object then how can we use the st_rgb() function if the bands are in BGR order?

Edit1: In terra::plotRGB() we can specify the indices of each band.

Edit2: Probably best to use st_downsample() to load a low resolution raster into memory and then select RGB bands?

[edzer]

I see your point (and the st_rgb docs suggest this); FYI plot.stars() has an rgb argument that lets you specify band indices, like c(3,2,1) if they come as BGR.

[kadyb]

Thanks! So I suggest 2 things:

1. Add the information to the st_rgb() documentation like: Alternatively, you can use plot() function with the rgb argument to create a three-band composition.
2. However, it might be worth leaving the error massage you made in the above commit, because maybe someone will also encounter this issue.

[edzer]

2: yes, but it didn't work, and seems much more complicated than I thought.

[kadyb]

2: yes, but it didn't work, and seems much more complicated than I thought.

Okay, I didn't check. I suspect that e.g. x[,,,c(2, 4, 6)] can also be very problematic.