Remove class from columns of class 'unit'

[ateucher]

When sf calculates the area or length of a feature, it gives the resulting object the 'units' class (from the units package). In geoojsonio::to_json (here) we should detect these and as.numeric them before converting to json. Or we could set force = TRUE in jsonlite::toJSON ?

library(sf)
#> Linking to GEOS 3.5.0, GDAL 2.1.1, proj.4 4.9.3
library(geojsonio)
#> 
#> Attaching package: 'geojsonio'
#> The following object is masked from 'package:base':
#> 
#>     pretty

file <- system.file("examples", "california.geojson", package = "geojsonio")
sf_obj <- read_sf(file)

## No problem
foo <- geojson_json(sf_obj)

## Creates an area column of class 'units'
sf_obj$area <- st_area(sf_obj)

class(sf_obj$area)
#> [1] "units"

geojson_json(sf_obj)
#> Error: No method asJSON S3 class: units

Session info

``` r devtools::session_info() #> Session info ------------------------------------------------------------- #> setting value #> version R version 3.4.0 (2017-04-21) #> system x86_64, mingw32 #> ui RTerm #> language (EN) #> collate English_Canada.1252 #> tz America/Los_Angeles #> date 2017-05-29 #> Packages ----------------------------------------------------------------- #> package * version date source #> backports 1.1.0 2017-05-22 CRAN (R 3.4.0) #> base * 3.4.0 2017-04-21 local #> compiler 3.4.0 2017-04-21 local #> curl 2.6 2017-04-27 CRAN (R 3.4.0) #> datasets * 3.4.0 2017-04-21 local #> DBI 0.6-1 2017-04-01 CRAN (R 3.4.0) #> devtools 1.13.1 2017-05-13 CRAN (R 3.4.0) #> digest 0.6.12 2017-01-27 CRAN (R 3.4.0) #> evaluate 0.10 2016-10-11 CRAN (R 3.4.0) #> foreign 0.8-68 2017-04-24 CRAN (R 3.4.0) #> geojsonio * 0.3.2 2017-02-06 CRAN (R 3.4.0) #> geosphere 1.5-5 2016-06-15 CRAN (R 3.4.0) #> graphics * 3.4.0 2017-04-21 local #> grDevices * 3.4.0 2017-04-21 local #> grid 3.4.0 2017-04-21 local #> htmltools 0.3.6 2017-04-28 CRAN (R 3.4.0) #> httr 1.2.1 2016-07-03 CRAN (R 3.4.0) #> jsonlite 1.4 2017-04-08 CRAN (R 3.4.0) #> knitr 1.16 2017-05-18 CRAN (R 3.4.0) #> lattice 0.20-35 2017-03-25 CRAN (R 3.4.0) #> magrittr 1.5 2014-11-22 CRAN (R 3.4.0) #> maptools 0.9-2 2017-03-25 CRAN (R 3.4.0) #> memoise 1.1.0 2017-04-21 CRAN (R 3.4.0) #> methods * 3.4.0 2017-04-21 local #> R6 2.2.1 2017-05-10 CRAN (R 3.4.0) #> Rcpp 0.12.11 2017-05-22 CRAN (R 3.4.0) #> rgdal 1.2-7 2017-04-25 CRAN (R 3.4.0) #> rgeos 0.3-23 2017-04-06 CRAN (R 3.4.0) #> rmarkdown 1.5.9000 2017-05-16 Github (rstudio/rmarkdown@0f89945) #> rprojroot 1.2 2017-01-16 CRAN (R 3.4.0) #> sf * 0.4-3 2017-05-15 CRAN (R 3.4.0) #> sp 1.2-4 2016-12-22 CRAN (R 3.4.0) #> stats * 3.4.0 2017-04-21 local #> stringi 1.1.5 2017-04-07 CRAN (R 3.4.0) #> stringr 1.2.0 2017-02-18 CRAN (R 3.4.0) #> tools 3.4.0 2017-04-21 local #> udunits2 0.13 2016-11-17 CRAN (R 3.4.0) #> units 0.4-4 2017-04-20 CRAN (R 3.4.0) #> utils * 3.4.0 2017-04-21 local #> V8 1.5 2017-04-25 CRAN (R 3.4.0) #> withr 1.0.2 2016-06-20 CRAN (R 3.4.0) #> yaml 2.1.14 2016-11-12 CRAN (R 3.4.0) ```

[ateucher]

I lean towards the latter for simplicity, and would deal with other special classes that come along. I can't think of a reason off the top of my head what the downsides would be... thoughts @sckott?

[sckott]

Agree forcing sounds good!

[ateucher]

Closed in a91a7b9d8faeccc12ca8ecf3d6e09f3fc6b6ccc5

[ateucher]

@sckott now it's really done I think, if you want to have a look. writeOGR doesn't like special classes either, so I tackled that in https://github.com/ropensci/geojsonio/commit/ba495356b219c4b92f5b97afcfe4bb9115b4793b

[sckott]

LGTM

[mdsumner]

Might be worth putting that classes logic into rgdal itself, I'll have a look. Roger patched the dev version recently to accept a tibble (it was otherwise relying on drop = TRUE).

[ateucher]

Thanks @mdsumner. It is explicitly documented in the help page for writeOGR that anything other than those basic classes will throw an error, so it seems they wanted the user to decide what to do with special classes

[mdsumner]

That's a good point, but I think the opportunities for this to be a problem are much more frequent now that the perspectives are changing. :)

[ateucher]

That's probably true! I certainly have no issues if you want to pursue it 😄

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