[R-sig-Geo] df with embedded wkt lists to sf

[Josiah Parry]

Furthermore, if you want to get these points into a linstring you can
combine the points by group (comment) and then cast them to a line like so
below.

This is an interesting use case! Thanks for introducing me to it.

dat_sf |>
  dplyr::group_by(comment) |>
  dplyr::summarise(geometry = sf::st_cast(
    sf::st_combine(geometry), "LINESTRING"
    ))

On Thu, Jun 9, 2022 at 4:34 PM Josiah Parry <josiah.parry using gmail.com> wrote:

> Hey Tim,
>
> The key thing here is to separate the long / lat points into elements in a
> vector. You can do this with a string split. Afterwards, separate these
> into their own rows like I've done below.
>
> I think this should get you on the right path!
>
>
> dat <- dget(textConnection(txtString))
>
> dat |>
>   tidyr::unnest(c(longitude, latitude)) |>
>   dplyr::mutate(longitude = strsplit(longitude, "; "),
>                 latitude = strsplit(latitude, "; ")) |>
>   tidyr::unnest(c(longitude, latitude)) |>
>   sf::st_as_sf(coords = c(2, 3), crs = 4326)
>
> On Thu, Jun 9, 2022 at 3:48 PM Howard, Tim G (DEC) via R-sig-Geo <
> r-sig-geo using r-project.org> wrote:
>
>> Howdy all -
>> There's probably a way to do this much​ more simply than I've figured it
>> out, so it's a bit embarrassing but here goes. I'm getting data out of a
>> shiny app that looks like the following, with lists of coordinates within
>> separate longitude and latitude columns.
>>
>> Is there more efficient way to get an `sf` collection than what I've got?
>> Perhaps an `apply` replacement for the for() loop? Using a tibble because
>> that's how `googlesheets4` gives it to me.
>>
>> # set up a couple of lines strings. lists within data.frame/tibble
>> txtString <- 'structure(list(comment = c("line one", "line two"),
>> longitude = list("-115.138577; -114.942454; -114.170219", "-118.411382;
>> -118.153971; -117.83527; -117.246901; -117.026262; -117.185613"),
>> latitude = list("37.527588; 38.234088; 38.368805", "41.296472; 41.645606;
>> 41.819467; 41.837741; 41.590604; 41.333312")),
>> row.names = c(NA, -2L), class = c("tbl_df", "tbl", "data.frame"))'
>>
>> dat <- dget(textConnection(txtString))
>>
>> # function for parsing the text strings
>> getWKT <- function(x){
>>   st_linestring(matrix(
>>     c(as.numeric(unlist(strsplit(x$longitude[[1]],";"))),
>>       as.numeric(unlist(strsplit(x$latitude[[1]],";")))),
>>     byrow = FALSE, ncol = 2)
>>   )
>> }
>>
>> # populate dataframe/tibble by going back to sf text
>> dat$wkt <- NA
>> for(i in 1:nrow(dat)){
>>   dat$wkt[[i]] <- st_as_text(getWKT(dat[i,]))
>> }
>>
>> # finally make the sf collection
>> dat_sf <- st_as_sf(dat, wkt = "wkt", crs = 4326)
>>
>>
>> Thanks in advance for any tips.
>> Tim
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo using r-project.org
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>

	[[alternative HTML version deleted]]