[R-sig-Geo] Raster stream network to lines

[Joseph Stachelek]

Hi Andy,

I have posted some code showing one way of doing this
with the `sf` package:

https://gist.github.com/jsta/d8d8e8d79877c720b6842ae8efa2
b9b8

If you are doing this a lot I recommend picking up GRASS:

https://grasswiki.osgeo.org/wiki/R.stream.*_modules
https://grass.osgeo.org/grass74/manuals/r.to.vect.html

--Joe

-----Original Message-----
From: Andy Bunn <Andy.Bunn at wwu.edu>
To: R-sig-Geo <r-sig-geo at r-project.org>
Subject: [R-sig-Geo] Raster stream network to lines
Date: Wed, 18 Apr 2018 19:03:21 +0000

I have a raster of streams with 0 being non-stream and 1
being stream. Is there a way to convert this into a
SpatialLinesDataFrame? rasterToContour() almost does what
I want but fails to draw the line on queens rules, etc.
Example here:

library(raster)
foo <- matrix(0,ncol=9,nrow=9)
foo[1:4,3] <- 1
foo[5,4] <- 1
foo[6:9,5] <- 1
foo <- raster(foo)
plot(foo)
bar <- rasterToContour(foo,nlevels=1)
plot(bar)

How can I get a continuous line in this example? Many
thanks, Andy

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