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
data(veronica)
coord2dist(coordmatrix=veronica.coord[1:20,], cut=20, file.format="decimal2",neighbors=TRUE)
[Package
prabclus version 2.2-2
Index]