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Check the format of coordinate columns

Source: R/latlong_format.R
latlong_format.Rd

Detects and reports the coordinate format – decimal degrees, DMS (DDdeg.MM'SS''}), or base-60 (\code{DDdeg.MM') – of values in one or more columns. Combined columns (latitude and longitude stored as a single delimited string) are split before format detection. Results are returned as a named list, one element per column.

Usage

latlong_format(data, columns, sep = ",", drop_na = TRUE)

Arguments

data

A data frame containing coordinate columns.

columns

Column name or c() of column names to check, supplied either unquoted (lat) or quoted ("lat").

sep

Character. Separator used to split combined coordinate columns before format detection. Default is ",".

drop_na

Logical. If TRUE, values that do not match any recognized coordinate format are excluded before summarizing results. Default is TRUE.

Value

A named list with one element per column in columns. Each element is itself a named list with two components:

format

Character vector of detected format names present in the column. One or more of "decimal", "dms", "base60". Returns "unknown" if no values match any recognised format (or if all values are excluded by drop_na).

counts

Integer vector of the same length as format, giving the number of values matching each detected format.

Details

The three recognised coordinate formats are:

  • Decimal degrees: "-12.345" or "51.5"

  • DMS: "12deg.34'56''N"

  • Base-60: "12deg.34'N"

A column may return multiple formats if values are inconsistently formatted – for example, a mix of decimal and DMS entries. This is reported rather than resolved, allowing the user to decide how to handle mixed formats before passing columns to latlong_combine or latlong_split.

Combined columns (those containing sep) are detected automatically and split before format checking, so the same sep used in latlong_combine or latlong_split should be passed here for consistent results.

See also

latlong_column for detecting which columns in a data frame contain coordinates,

latlong_combine for merging separate coordinate columns into one,

latlong_split for splitting a combined coordinate column into separate latitude and longitude columns,

latlong_filter for removing invalid coordinates after checking formats,

latlong_convert for converting coordinate formats after checking.

Examples

df <- data.frame(
  id  = 1:4,
  lat = c("51.5", "48.8", "40.7", "35.6"),
  lon = c("-0.1", "2.3", "-74.0", "139.7")
)

# Check format of a single column
latlong_format(df, lat)
#> $lat
#> $lat$format
#> [1] "decimal"
#> 
#> $lat$counts
#> [1] 4
#> 
#> 

# Check multiple columns at once
latlong_format(df, c(lat, lon))
#> $lat
#> $lat$format
#> [1] "decimal"
#> 
#> $lat$counts
#> [1] 4
#> 
#> 
#> $lon
#> $lon$format
#> [1] "decimal"
#> 
#> $lon$counts
#> [1] 4
#> 
#> 

# Mixed formats in one column
df_mixed <- data.frame(
  coords = c("51.5", "48deg.52'N", "40.7", "35deg.36'00''N")
)
latlong_format(df_mixed, coords)
#> $coords
#> $coords$format
#> [1] "decimal" "dms"     "base60" 
#> 
#> $coords$counts
#> [1] 2 1 1
#> 
#> 

# Combined latitude-longitude column with custom separator
df_combined <- data.frame(
  latlon = c("51.5;-0.1", "48.8;2.3", "40.7;-74.0")
)
latlong_format(df_combined, latlon, sep = ";")
#> $latlon
#> $latlon$format
#> [1] "decimal"
#> 
#> $latlon$counts
#> [1] 6
#> 
#> 

# Include unknown-format values in counts
df_dirty <- data.frame(
  lat = c("51.5", "not_a_coord", "40.7", NA)
)
latlong_format(df_dirty, lat, drop_na = FALSE)
#> $lat
#> $lat$format
#> [1] "decimal"
#> 
#> $lat$counts
#> [1] 2
#> 
#>