rbindlist() with list of sf objects doesn't combine different geometries
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Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 45/100
Research direction
Start by running the supplied R example with data.table::rbindlist() and the split sf objects. Inspect the rbindlist() handling of class attributes on the geometry column and compare it with do.call(rbind, st.split). Done means the reported differing-geometry case combines without the current class-mismatch error while preserving the expected result.
Written by the indexing model from the issue text.
Description
I've check the NEWS/issues/stack overflow but not seen any mentions of rbindlist() in connection with this issue.
I want to make use of data.table's amazing speed :) in combining sf dataframes as in this example here, issue #798
However, when different geometries are involved, an error is returned on different class attributes of the geometry column in the sf dataframe. Here is a simple example:
library(sf)
# create a sf data frame with different geometries
st <- st_as_sf(data.frame(
id = 1:2,
geometry = st_as_sfc(c("LINESTRING(10 5, 9 4, 8 3, 7 2, 6 1)",
"MULTILINESTRING ((0 3, 0 4, 1 5, 2 5), (0.2 3, 0.2 4, 1 4.8, 2 4.8), (0 4.4, 0.6 5))"))))
st
# split into list
st.split <- split(st, ~id)
# attempt to recombine with rbindlist() - error
st2.dt <- data.table::rbindlist(st.split)
# Error in data.table::rbindlist(st.split) :
# Class attribute on column 2 of item 2 does not match with column 2 of item 1.
# rbind does work:
st2.rbind <- do.call(rbind, st.split)
st2.rbind
# Is data table checking these classes?
lapply(st.split, function(x) class(x$geometry))
A workaround can be to use st_cast() to unify geometries (eg to LINESTRING here, or more generally GEOMETRYCOLLECTION) but this is not alway practical.
Can this check on classes be changed for sf objects so that different geometries can be combined?
# Output of sessionInfo()
R version 4.2.1 (2022-06-23 ucrt)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19044)
Matrix products: default
locale:
[1] LC_COLLATE=English_United Kingdom.utf8 LC_CTYPE=English_United Kingdom.utf8 LC_MONETARY=English_United Kingdom.utf8
[4] LC_NUMERIC=C LC_TIME=English_United Kingdom.utf8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] sf_1.0-8
loaded via a namespace (and not attached):
[1] Rcpp_1.0.9 rstudioapi_0.14 magrittr_2.0.3 units_0.8-0 tidyselect_1.1.2 R6_2.5.1 rlang_1.0.5
[8] fansi_1.0.3 dplyr_1.0.9 tools_4.2.1 grid_4.2.1 compare_0.2-6 data.table_1.14.2 KernSmooth_2.23-20
[15] utf8_1.2.2 cli_3.3.0 e1071_1.7-11 DBI_1.1.3 class_7.3-20 assertthat_0.2.1 tibble_3.1.8
[22] lifecycle_1.0.1 purrr_0.3.4 vctrs_0.4.1 glue_1.6.2 proxy_0.4-27 compiler_4.2.1 pillar_1.8.1
[29] generics_0.1.3 classInt_0.4-7 pkgconfig_2.0.3
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