[R-sig-Geo] Overlay spatial lines on raster

[Robert J. Hijmans]

How about something like:

library(raster)
r = linesToRaster(xter, xterpdata, field = "ID" )
v = zonal(xterpdata, r, mean)

v now shold has the mean value of the raster for each line ID and you
can merge those back


On Fri, Jan 29, 2010 at 9:54 AM, Agustin Lobo <alobolistas at gmail.com> wrote:
> Partially answering myself:
> This is what I've done until now:
>
> xter <-
> readOGR(dsn="/media/Transcend/PROVI/MARICEL2/x_terRiverBasin",layer="x_ter")
>> class(xter)
> [1] "SpatialLinesDataFrame"
> attr(,"package")
> [1] "sp"
>
> xterp <- coordinates(xter)
> xterp <- sapply(xterp, function(x) do.call("rbind", x))
> xterp <- do.call("rbind",xterp)
>
> as told by Roger.
>
> Now:
> require(raster)
> r <- raster("test.tif")
> xterpdata <- xyValues(r,xterp)
> xterp2 <- data.frame(utmx=xterp[,1], utmy=xterp[,2], NO3_2007=xterpdata)
> coordinates(xterp2) <- c("utmx", "utmy")
>
> So I get to step 2, but don't see how to convert from the points
> to the lines again (to get xterl). The problem is that when I did:
> xterp <- sapply(xterp, function(x) do.call("rbind", x))
> xterp <- do.call("rbind",xterp)
>
> I lost the IDs of the lines. So I would need to keep the IDs of the lines
> for each point in the result of
> coordinates() to be able of going back to the lines once I've put the raster
> values in the data slot of the xterp
>
> I'll keep on, but any help would be much appreciated.
>
> Agus
>
> 2010/1/29 Agustin Lobo <alobolistas at gmail.com>
>
>> Hi!
>>
>> My goal is to colorcode a river network according to the values of
>> a raster map (which comes from an interpolation). The spatial lines are
>> imported
>> from a shapefile. The raster could be imported or I could run the
>> interpolation in R.
>>
>> As what I'm planing could be rather involved, I prefer asking before:
>>
>> 1. Convert spatial lines to spatial points as discussed earlier this week.
>> 2. Overlay points on the raster and get the values for the points in a
>> Spatial Points Data Frame
>> 3. Convert the Spatial Points Data Frame into Spatial Lines Data Frame
>> 4. writeOGR() to shapefile.
>>
>> The main question is: is the data frame of the points going to be
>> transferred to the lines
>> at step 3?
>>
>> THnaks
>>
>> Agus
>>
>
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