spatvectorcollection does not behave as a list

[jedgroev]

I do like that there is a class of spatvectorcollection, however, the functionality is not exactly what I expected. I would expect it to behave as a list (and thus similar to a spatraster with multiple bands). There are two issues:

(ISSUE 1): list names are not inherited and added automatically to the collection (minor)
(ISSUE 2): spatvectorcollection cannot be filtered using the names of the datasets

I am using terra 1.7.71, the most recent version available on CRAN.

Here is an example:

library(terra)
terra 1.7.71

# sample data
f <- system.file("ex/lux.shp", package="terra")
v <- vect(f)
# create two vector datasets
v <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 < 4") 
v2 <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 > 5")

# make list of the two vector datasets 
v_list <- list(v,v2)
names(v_list) <- c('A0','A1')

# make collection 
collection <- svc(v_list)

# (ISSUE 1) I would have expected that the names would be inherited from the names given to each item in the list
# add names to collection 
names(collection) <- names(v_list)

# (ISSUE 2) It is not possible to subset a collection by using the names of the datasets within the collection
collection$A1
Error in collection$A1 : $ operator not defined for this S4 class

names(collection)
[1] "A0" "A1"

[rhijmans]

Thanks, I now get

library(terra)
#terra 1.7.79
f <- system.file("ex/lux.shp", package="terra")
v1 <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 < 4") 
v2 <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 > 5")
v_list <- list(A0=v1, A1=v2)
collection <- svc(v_list)

names(collection)
#[1] "A0" "A1"
collection$A1
# class       : SpatVector 
# geometry    : polygons 
# dimensions  : 7, 3  (geometries, attributes)
# extent      : 5.810482, 6.528252, 49.44781, 49.85403  (xmin, xmax, ymin, ymax)
# source      : lux.shp
# coord. ref. : lon/lat WGS 84 (EPSG:4326) 
# names       :       NAME_1       NAME_2  ID_2
# type        :        <chr>        <chr> <num>
# values      : Grevenmacher   Echternach     6
#               Grevenmacher       Remich     7
#               Grevenmacher Grevenmacher    12

[jedgroev]

I just noticed that plotting the collection is also not possible:

library(terra)
#terra 1.7.79
f <- system.file("ex/lux.shp", package="terra")
v1 <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 < 4") 
v2 <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 > 5")
v_list <- list(A0=v1, A1=v2)
collection <- svc(v_list)
terra::plot(collection)
Error in as.double(y) : 
  cannot coerce type 'S4' to vector of type 'double'