R: Geographical coordinates to distances

coord2dist {prabclus} | R Documentation

## Geographical coordinates to distances

### Description

Computes geographical distances from geographical coordinates

### Usage

      coord2dist(file=NULL, coordmatrix=NULL, cut=NULL,
                           file.format="degminsec",
                           output.dist=FALSE, radius=6378.137,
                  fp=1/298.257223563, neighbors=FALSE)

### Arguments

`file` | string. A filename for the coordinate file. The file should have 2, 4 or 6 numeric columns and one row for each location. See `file.format`. One of `file` and `coordmatrix` needs to be specified (if `coordmatrix` is not specified, coordinates are read from `file`).
`coordmatrix` | something that can be coerced into a matrix with 2, 4 or 6 columns. Matrix of coordinates, one row for each location. See `file.format`. One of `file` and `coordmatrix` needs to be specified.
`cut` | numeric. Only active if `neighbors==TRUE`; see `neighbors`.
`file.format` | one of `"degminsec"`, `"decimal2"` or `"decimal4"`. The format of the required file or `coordmatrix` consists of the following columns: "degminsec" 6 columns; the first three give degrees, minutes and seconds for latitude, columns 4-6 the same for longitude. Values in column 1 and 4 can be positive or negative (negative means "South", "West", respectively). Values in the other columns should be non-negative. "decimal2" 2 columns; the first one gives latitude, the second one longitude in proper decimal notation. Values can be positive or negative (negative means "South", "West", respectively). "decimal4" 4 columns; the first two give latitude, no. 3 and 4 give longitude. Values in column 1 and 3 can be positive or negative (negative means "South", "West", respectively). The give integer degrees. Values in the other columns should be non-negative. They give percentages (`<=100`).
`output.dist` | logical. If `TRUE`, the resulting distance matrix is given out as a `dist` object.
`radius` | numeric. Radius of the earth in km used in computation (the default is the equatorial radius but this is not the uniquely possible choice).
`fp` | flattening of the earth; the default is from WGS-84.
`neighbors` | logical. If `TRUE`, a neighborhood list is also computed, listing for every location all locations with distance `<=cut` as neighbors.

### Value

If `neighbors==TRUE`, a list with components

`distmatrix` | distance matrix between locations. See `output.dist` above. This is in km by default; the measurement unit is determined by the value used for `radius`.
`nblist` | list with a vector for every location containing the numbers of its neighbors, see `neighbors`.

If `neighbors==FALSE`, only the distance matrix.

### Author(s)

Christian Hennig chrish@stats.ucl.ac.uk http://www.homepages.ucl.ac.uk/~ucakche

### References

German Wikipedia from 29 August 2010: http://de.wikipedia.org/wiki/Orthodrome

### See Also

`geo2neighbor`

### Examples

      options(digits=4)
      data(veronica)
      coord2dist(coordmatrix=veronica.coord[1:20,], cut=20, file.format="decimal2",neighbors=TRUE)

[Package prabclus version 2.2-6 Index]