[R-sig-Geo] package sp, extract values points-lines

[Roger Bivand]

On Thu, 24 Nov 2016, rolandh at uni-muenster.de wrote:

> Hi Marta,
>
> by ?sp::over you will see that SpatialLines are not supported.
>
> Moreover it says:
> "over methods that involve SpatialLines objects, or pairs of SpatialPolygons require package rgeos, and use gIntersects."
>
> So, try gIntersects ...

Right, and note that the precision model will bite painfully (the points 
may appear to be on the lines, but given the precision model may not 
actually intersect in the default representation (think one thousandth of 
a millimetre). You may need to buffer either points or lines to get the 
intersections you expect.

Roger

>
> Cheers,
> Roland
>
> marta azores schrieb am 2016-11-24:
>> Hi everyone,
>
>> I need to join two datasets, one with survey boats and other with
>> sightings. There are different boats in the same area.
>> First I've created the tracks with the gps information, and give to each
>> track an ID number(column) .
>> Second, I would like to join by time and space the sightings with the track
>> of the boats.
>> I'm trying the"over" function of the package sp.
>
>> The first test was try to join only by space, but the function say there
>> aren't overlap. I don't know why, because the points of the sightings are
>> over the line.
>
>> Any idea?
>> Thanks in advance
>> Marta
>
>> #boat data
>> boat <- read.table("path/.csv", header=TRUE, sep=",", na.strings="NA",
>> dec=".", strip.white=TRUE)#
>> boatdf<-as.data.frame(boat)
>> #sighting data
>> sght <- read.table("path/.csv.csv", header=TRUE, sep=",", na.strings="NA",
>> dec=".", strip.white=TRUE)#
>
>> #Spatial points
>> #sightings
>> Sxy = cbind(sght$LONG,sght$LAT)
>> Spts = SpatialPoints(Sxy)
>> sghtdf<-as.data.frame(sght)
>> #boats
>> xy = cbind(boat$Long1,boat$Lat1)
>> pts = SpatialPoints(xy)
>
>> # dataframe
>> ptsdf = SpatialPointsDataFrame(pts, boatdf)#data frame barcos
>> Sptsdf = SpatialPointsDataFrame(Spts, sghtdf)#data frame species
>
>> #Line
>> line<-as(ptsdf, "SpatialLines")
>
>> #
>> #extract values
>> over(Sptsdf, line)# NA?
>
>> 	[[alternative HTML version deleted]]
>
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-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
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