selpos: Geographical point selection.
In geo: Draw and Annotate Maps, Especially Charts of the North Atlantic

Description Usage Arguments Details Value See Also Examples

Select geographical data points by arbitrary criterion.

1	selpos(lat, lon = NULL, ind)

`lat`	Latitude of points or list containing lat,lon.
`lon`	Longitude of data points. If missing, this must be part of the lat argument.
`ind`	Selection criterion.

The normal way of working with geographical data is to store positions as a list with names lat and lon. This is easier for most applications, except selection of subsets, where it is essential to access individual elements. The purpose of this routine is merely to ease the selection process.

Returns list with elements lat,lon which satisfy the criterion.

geoplot,

## Not run: 
             subs<-selpos(pos,,z>6)# Select positions where z>6

       The Function is trivially defined as
       function(lat, lon = NULL, ind)
       {
                      if(is.null(lon)) {
                           lon <- lat$lon
                           lat <- lat$lat
                      }
                      lat <- lat[ind]
                      lon <- lon[ind]
                      return(lat, lon)
       }

## End(Not run)