[R] flow map lines between point pairs (latitude/longitude)

[Ray Brownrigg]

Here's one solution, YMMV:
library(maps)
# Note, plot the map first to get the aspect ratio (or projection) right
map("county", xlim=range(df2VisitTrips[, c(5, 7)]), ylim=range(df2VisitTrips[, c(4, 6)]), 
col=8)
map("state", add=T)
map.axes()
for (i in 1:length(df2VisitTrips[, 1])) {
  lines(df2VisitTrips[i, c(5, 7)], df2VisitTrips[i, c(4, 6)], lwd=0.2 + df2VisitTrips[i, 
3]/10, col=i+1)
}

Ray Brownrigg

On Thu, 03 Jul 2008, Richard and Barbara Males wrote:
> I have a dataset giving traffic between pairs of ports, and the
> lat/lon of each port, roughly as follows:
>
> sample data as follows
>
> > df2VisitTrips[1:4,]
>
>   Origin Destination NumberOfTrips OriginLatitude OriginLongitude
> DestinationLatitude DestinationLongitude
> 1     P1         P16             1               39.45965
> -80.15633        40.76111            -79.54583
> 2     P1          P3              1               39.45965
> -80.15633        39.58861            -79.98222
> 3   P102        P108          19              36.98210       -88.21597
>        37.19667            -88.84389
> 4   P102        P109           71              36.98210
> -88.21597       37.09472            -89.13694
>
>
> I am interested in plotting variable-width lines, based on
> NumberOfTrips, between point pairs (OriginLongitude,OriginLatitude)
> and (DestinationLongitude,DestinationLatititude), e.g. a flow map
> between the ports.  At some point, I may wish to add an underlay base
> map (say counties in the US), but that is not critical at this time.
>
> There seem to be many packages in R that deal with spatial data (sp,
> maps, PBSMapping, etc.), but it is unclear to me which one would work
> best for this application.
>
> Any advice gratefully appreciated.
>
> R. Males
> Cincinnati, Ohio, USA
>
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