Extract or Replace Parts of a Coords Object

Extract or replace subsets of coords.

Usage

# S3 method for class 'coords'
x[i]

# S3 method for class 'coords'
x[i] <- value

Arguments

x: a "coords" object.
i: indices specifying elements to extract or replace—see Extract.
value: a numeric, a numeric vector of coordinate values of length(i), or a "coords" object, possibly named.

Value

a "coords" object.

Details

Subsetting a "coords" object (except by an empty index) will drop all attributes except fmt, latlon, names and valid. Indices referencing values greater than length(x) will throw a subscript out of bounds error. If names are not required, use unname(), see examples.

Replacement values may be a single numeric, a numeric vector of coordinate values of length(i), or a "coords" object, possibly with a "latlon" attribute. However, the "latlon" attribute of the replacement value is ignored if the "coords" object x has no corresponding attribute set. If replacement values are named, the names are also ignored; to replace names, use names<-() replacement form.

Note

To extract and replace subsets of "waypoints" objects, simply use the base package [ and [<- operators, taking care not to exclude the latitude and longitude columns or "Name" column (if present), which could lead to undefined results.

Examples

## Continuing example from `as_coords()`...

## Named "coords" object in degrees and minutes with
## eight values each of latitude and longitude
dm
#> Nelson's Column                           51°30.4659′ N
#> Ostravice                                 49°32.7726′ N
#> Tally Ho                                  48°06.4339′ N
#> Washington Monument                       38°53.3696′ N
#> Null Island                                0°00.0000′ N
#> Tristan da Cunha                          37°06.7044′ S
#> Mawson Peak                               53°06.2869′ S
#> Silvio Pettirossi International Airport   25°14.4093′ S
#> Nelson's Column                            0°07.6754′ W
#> Ostravice                                 18°23.9137′ E
#> Tally Ho                                 122°46.7203′ W
#> Washington Monument                       77°02.1145′ W
#> Null Island                                0°00.0000′ E
#> Tristan da Cunha                          12°17.3178′ W
#> Mawson Peak                               73°31.0370′ E
#> Silvio Pettirossi International Airport   57°31.1536′ W

## Extract the first eight values
dm[1:8]
#> Nelson's Column                           51°30.4659′ N
#> Ostravice                                 49°32.7726′ N
#> Tally Ho                                  48°06.4339′ N
#> Washington Monument                       38°53.3696′ N
#> Null Island                                0°00.0000′ N
#> Tristan da Cunha                          37°06.7044′ S
#> Mawson Peak                               53°06.2869′ S
#> Silvio Pettirossi International Airport   25°14.4093′ S

## Exclude the first eight values
dm[-8:0]
#> Nelson's Column                            0°07.6754′ W
#> Ostravice                                 18°23.9137′ E
#> Tally Ho                                 122°46.7203′ W
#> Washington Monument                       77°02.1145′ W
#> Null Island                                0°00.0000′ E
#> Tristan da Cunha                          12°17.3178′ W
#> Mawson Peak                               73°31.0370′ E
#> Silvio Pettirossi International Airport   57°31.1536′ W

## Index odd-numbered values
(index <- as.logical(1:16 %% 2))
#>  [1]  TRUE FALSE  TRUE FALSE  TRUE FALSE  TRUE FALSE  TRUE FALSE  TRUE FALSE
#> [13]  TRUE FALSE  TRUE FALSE
dm[index]
#> Nelson's Column   51°30.4659′ N
#> Tally Ho          48°06.4339′ N
#> Null Island        0°00.0000′ N
#> Mawson Peak       53°06.2869′ S
#> Nelson's Column    0°07.6754′ W
#> Tally Ho         122°46.7203′ W
#> Null Island        0°00.0000′ E
#> Mawson Peak       73°31.0370′ E

## Extract values without names
unname(dm)[1:4]
#>  51°30.4659′ N
#>  49°32.7726′ N
#>  48°06.4339′ N
#>  38°53.3696′ N

## Create "coords" object with updated position of Tally Ho
newpos <- as_coords(c(4930.342, -12411.580), fmt = 2)
latlon(newpos) <- c(TRUE, FALSE)
newpos
#>  49°30.3420′ N
#> 124°11.5800′ W

## Update position using the "coords" object as replacement value
dm[c(3, 11)] <- newpos
dm[c(3, 11)]
#> Tally Ho   49°30.3420′ N
#> Tally Ho  124°11.5800′ W

## Or, as latlon didn't actually change, use simple numeric vector
dm[c(3, 11)] <- c(4930.342, -12411.580)
dm[c(3, 11)]
#> Tally Ho   49°30.3420′ N
#> Tally Ho  124°11.5800′ W

rm(dm, index, newpos)