grid overlay on polylines
Lee, What are you trying the accomplish with this "overlay"? If you want to do a spatial query (extract grid cell values covered by the line), you can use raster::extract. If you want to rasterize (create a raster where the cells covered by the line get a particular value), you can use raster::rasterize. Robert
On Mon, Nov 25, 2013 at 1:15 PM, <ldecola at comcast.net> wrote:
i'm trying to overlay a grid on a SpatialLines object but over() doesn't work, even if i load rgeos...
--------
library(sp)
library(rgeos)
# SPATIAL LINES OBJECT
tmp_sl <- SpatialLines(
list(
Lines(
list(
Line(matrix(c(0, 1, 1, 0, 0, 1), 3))
),
ID = 'a'
)
)
)
plot(tmp_sl, axes = T, col = 'red', lwd = 4)
# SPATIAL GRID TO COVER IT
res <- 2^-3
tmp_grd <- SpatialGrid(
GridTopology(
bbox(tmp_sl)[, 'min'],
rep(res, 2),
round(apply(bbox(tmp_sl), 1, diff) / res + 1)
)
)
plot(tmp_grd, add = T)
# DOESN'T WORK...
over(tmp_grd, tmp_sl)
# *** END ***
--------
Lee De Cola, PhD, MCP.
DATA to Insight
LDECOLA at COMCAST.NET
Reston, Virginia
703 709 6972
571 315 0577 mobile
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