[R-sig-Geo] shortestPath in a loop

[Jérome Mathieu]

Hi,

Did you have a look at the package adehabitatLT?

https://cran.r-project.org/web/packages/adehabitatLT/vignettes/adehabitatLT.pdf

It deals with trajectories based on points ordered by date.

Jerome


2017-01-13 11:41 GMT+01:00 marta azores <martazores at gmail.com>:

> Thanks for your quick reply to my question,
>
> This ten points are ordered by time (date + time), and I know ,the points
> are all connected.  I didn't include the column with the time in this
> example, to make it simple.
>
> After read your messages, I was looking the minimum spanning tree for the
> vertices.
> The advantage with the function "shortestPath" is that you have as result a
> spatial line output, which I need it.
> However, the minimum spanning tree give as output an ordiplot.
>
> Is it possible to transform the ordiplot into spatialLines?
>
> Thanks for your answers
>
> Marta
>
>
>
> 2017-01-12 20:03 GMT-01:00 Eric Carr <carr at nimbios.org>:
>
> > Generically independent of R, A graph and the connectivity between points
> > needs defined before a shortest path algorithm can be applied.  If it
> > assumes all points are connected, than the shortest path will be a
> straight
> > line.  What you are looking for is some sort of  minimum spanning tree
> for
> > the vertices.
> > Eric
> >
> > On Thu, Jan 12, 2017 at 11:17 AM, marta azores <martazores at gmail.com>
> > wrote:
> >
> >> Dear forum members,
> >>
> >> I would like to know how join several points with the aim to track a
> ship.
> >>
> >> After reading the documentation of some packages, I decided to use the
> >> function shortestPath, but I only got the line between the first and the
> >> last location of my points list. I need the complete survey, including
> also
> >> the middle points. I try a loop to build the survey of the boats using
> >> their locations, but It didn't work to me.
> >>
> >>
> >> Any idea?
> >>
> >> Thanks in advance,
> >>
> >> Marta
> >>
> >> #script# it's also attached in a R.file: question loop2.R
> >> ##########################################################
> >> #
> >> #raster# it's attached
> >> azoTS1<- raster("C:/Users/Documents/azoTS1.tif")#wgs84
> >> #
> >> #10 points# it's attached
> >> boat <- read.table("C:/Users/Documents/10pontos.csv", header=TRUE,
> >> sep=",", na.strings="NA", dec=".", strip.white=TRUE)#
> >> head(boat)
> >>
> >> #raster to transitionlayer
> >> trCostS4<- transition(1/azoTS1, mean, directions=4)
> >>
> >> # points to spatialpointsdataframe
> >> x=boat$Long1
> >> y=boat$Lat1
> >> coords = cbind(x, y)
> >> plot(coords)
> >> sp = SpatialPoints(coords, proj4string=CRS("+proj=longlat +ellps=WGS84
> >> +datum=WGS84"), bbox = NULL)
> >> sp
> >> spdf=SpatialPointsDataFrame(sp,boat)
> >> spdf
> >> nrow(spdf)
> >> plot(sp,axes=TRUE)
> >> plot(spdf,add=TRUE, axes=TRUE)
> >>
> >> #shortestpath
> >>
> >> ## 1) this script only join the first point of the list and the last
> one,
> >> and the points in the middle are not used.
> >> CostpathSPdf <- shortestPath(trCostS4, spdf[1,], spdf[10,],
> >> output="SpatialLines")
> >> plot(CostpathSPdf,add=TRUE,axes=TRUE,col=2)#R_plot1.png (it's attached)
> >>
> >> ## 2) this script didn't work to me
> >>
> >> #first way from website: http://stackoverflow.com/quest
> >> ions/8127066/loop-or-sapply-function-for-multiple-least-
> >> cost-analysis-in-r?answertab=active#tab-top
> >> for(i in 1:nrow(spdf)) {
> >>   # Computation
> >>   Costpath <- shortestPath(trCostS4, spdf[i,], spdf[10,],
> >> output="SpatialLines")
> >>   plot(Costpath)
> >>
> >> }
> >>
> >> #Error in validObject(.Object) :
> >> #invalid class “SpatialLines” object: bbox should never contain infinite
> >> values
> >>
> >> _______________________________________________
> >> R-sig-Geo mailing list
> >> R-sig-Geo at r-project.org
> >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>
> >
> >
>
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-- 
Jérôme Mathieu <http://www.jerome-mathieu.com/>
Université Pierre & Marie Curie <http://www.upmc.fr/>
Institute of Ecology and Environmental Science (Paris)
<https://ieesparis.ufr918.upmc.fr/>
Team EERI

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