Split a combined coordinate column into separate columns

Splits a single combined coordinate column into separate latitude and longitude columns, appended to the data frame. The inverse of this operation is latlong_combine. Useful as a prerequisite for functions that require separate coordinate columns, such as latlong_range and latlong_region.

Usage

latlong_split(
  data,
  combined_col,
  latitude,
  longitude,
  sep = ",",
  drop_na = FALSE
)

Arguments

data

A data frame containing a combined coordinate column.

combined_col

Column name of the combined coordinate column containing latitude and longitude as a single delimited string (e.g. "51.5,-0.1"), supplied either unquoted (coords) or quoted ("coords").

latitude

Column name for the new latitude column to be appended, supplied either unquoted (lat) or quoted ("lat").

longitude

Column name for the new longitude column to be appended, supplied either unquoted (lon) or quoted ("lon").

sep

Character. Separator between latitude and longitude values in combined_col. Default is ",". Must match the separator used when the combined column was created.

drop_na

Logical. If TRUE, rows where splitting produces NA in either new column are dropped. Default is FALSE.

Value

The input data frame with two additional character columns appended, named according to latitude and longitude. The original combined_col is retained. Values are returned as character strings; use as.numeric() or latlong_convert if numeric decimal degree values are required downstream. A console message reports the number of rows removed when drop_na = TRUE.

Details

Splitting is performed by strsplit() on sep, with leading and trailing whitespace trimmed from each part. Rows where combined_col contains fewer than two parts after splitting produce NA in the longitude column. Input strings are converted to UTF-8 before splitting to handle encoded coordinate values.

The new coordinate columns are character type regardless of input format. Use latlong_format to verify the format of the split columns, and latlong_convert to convert to a target format before passing to other functions.

See also

latlong_combine for merging separate coordinate columns into a single combined column,

latlong_format for checking the format of the split columns,

latlong_convert for converting split columns to a target coordinate format,

latlong_range for filtering to a bounding box, which does not accept combined columns,

latlong_region for filtering to named geographic regions, which does not accept combined columns.

Examples

df <- data.frame(
  id     = 1:4,
  coords = c("51.5,-0.1", "48.8,2.3", "-33.9,151.2", "40.7,-74.0")
)

# Split into separate latitude and longitude columns
latlong_split(df, combined_col = coords, latitude = lat, longitude = lon)
#>   id      coords   lat   lon
#> 1  1   51.5,-0.1  51.5  -0.1
#> 2  2    48.8,2.3  48.8   2.3
#> 3  3 -33.9,151.2 -33.9 151.2
#> 4  4  40.7,-74.0  40.7 -74.0

# Use a custom separator
df_sep <- data.frame(
  coords = c("51.5;-0.1", "48.8;2.3", "-33.9;151.2")
)
latlong_split(df_sep, combined_col = coords, latitude = lat,
              longitude = lon, sep = ";")
#>        coords   lat   lon
#> 1   51.5;-0.1  51.5  -0.1
#> 2    48.8;2.3  48.8   2.3
#> 3 -33.9;151.2 -33.9 151.2

# Drop rows where splitting produces NA
df_na <- data.frame(
  coords = c("51.5,-0.1", "48.8", NA, "40.7,-74.0")
)
latlong_split(df_na, combined_col = coords, latitude = lat,
              longitude = lon, drop_na = TRUE)
#> [latlong_split] 2 NA row(s) removed
#>       coords  lat   lon
#> 1  51.5,-0.1 51.5  -0.1
#> 4 40.7,-74.0 40.7 -74.0

# Split then filter by bounding box
df |>
  latlong_split(combined_col = coords, latitude = lat, longitude = lon) |>
  latlong_range(latitude = lat, longitude = lon,
                lat_min = 0, lat_max = 60,
                lon_min = -10, lon_max = 40)
#> [latlong_range] 2 row(s) removed: 0 NA, 2 out of range
#>   id    coords  lat  lon
#> 1  1 51.5,-0.1 51.5 -0.1
#> 2  2  48.8,2.3 48.8  2.3