Importing and Handling DXF Map files in R
On Thu, 11 May 2006, Roger Bivand wrote:
On Thu, 11 May 2006, Paolo Cavallini wrote:
one possible way is passing through GRASS GIS (you need latest version from CVS, though). pc
Agreed, converting from DXF through OGR (as in the rgdal package for R) is not possible (http://www.remotesensing.org/gdal/ogr/drv_dxfdwg.html). Depending on platform, there may be converters available, but not unemcumbered. Since the data are said to be points, I wonder if Francisco or the originator of the data if not him, can dump it as ASCII from the CAD software - since there is no topology. A very good book that I certainly recommend is Bailey & Gatrell's Interactive Spatial Data Analysis - their treatment of point pattern analysis is easy to follow (including kernel densities), and most of their point pattern examples are replicated in the examples of the splancs package for R. I'm not sure how kernel2d scales for 70K points, though, and feel that you may find the hexbin package in bioconductor an alternative: it is something else, but is designed for lots of data: http://www.bioconductor.org/repository/devel/vignette/hexagon_binning.pdf and there seems to be a smoother there too.
Replying to my own question, kernel2d() scales brilliantly:
set.seed(1)
cores <- cbind(x=runif(300), y=runif(300))
out <- do.call("rbind", lapply(1:300, function(i)
cbind(x=cores[i,1]+rnorm(200, 0, runif(1, 0.001, 0.02)),
y=cores[i,2]+rnorm(200, 0, runif(1, 0.001, 0.02)))))
plot(out, pch=".")
plot(hexbin(out))
image(kernel2d(out, bboxx(bbox(out)), h0=0.05, 50, 50),
col=grey(99:1/100))
plot(hexbin()) 1.4 seconds
image(kernel2d()) 1.0 seconds
and the new spkernel2d() wrapper makes it convenient to stack up kernel
densities in a SpatialGridDataFrame and display with spplot().
Please let the list know how you decide to extract the point coordinates, others will benefit from your experience. Hope this helps, Roger
At 17:09, gioved? 11 maggio 2006, Francisco Javier Aguirre Navarro has probably written:
Hello, I am a newby in the filed of spatial data analysis, could you please point me to the right libraries/functions in R that allow me to import DXF maps and analize spatial data related to these maps ? I would appreciaiate any internet references or books that may give a good hands-on introduction to spatial data analysis, I have good knowledge of classical statistical methods. I need to analyze about 75000 data points scattered on a map area and I'd like to construct a "density" map of my variable of interest and eventually see how these densities change in time. Thank you very much for your help. Francisco J. Aguirre Bavaria, Bogota - Colombia.
Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: Roger.Bivand at nhh.no