On Thu, 7 Jan 2010, Noli Sicad wrote:
# Deleting shapefile polygons that doesn't much with record in the
merge dbf file
I have already told you to use "["
new_obj <- obj[keep,]
where keep may be an integer vector of row numbers, a logical vector of
TRUE/FALSE values, or (for newer versions of sp) a negative integer vector
of entities to drop. So maybe:
keep <- !is.na(obj$x)
As I said before, think of Spatial*DataFrame objects as data.frame objects
and use the same operators as a first approximation which will usually
work, as indeed it has to for Spatial*DataFrame objects to function as the
data= argument in the (formula, data) S language White Book abstraction
that underpins most analysis in S/R.
Roger
I want to do:
1. Delete polygons that doesn't have a match with record in joined /
merge table of the shapefile.
(Done transpose and merging - joined to one-to-one relationship already.)
2. Create a subset of the polygon and save shapefile or just save the
revise shapefile
3. Open in shapefile in QGIS and do spplot.
~~~~~~~~~~~~~~
from 1 to 93 polygon
if table ID == polygon_ID then print("Polygon OK")
else delete the polygon
How do I delete the polygon and save?
~~~~~~~~~~~~~
getwd()
setwd('C:\\Down2\\R_forestmgt\\modelIII\\')
library(rgdal)
forest <- readOGR(".", "ForestStand")
forest.dat <- slot(forest, "data") <------ is this necessary?
xlength<-nrow(forest.dat)
for (i in 1:xlength)
if (forest.dat$ID[x] == forest[ID[x] {print("Polygon OK")
} else { Delele Polygon}
writeOGR(forest, ".", "ForestStandNew", "ESRI Shapefile")
~~~~~~~~~~~~~~~~~
The script above doesn't run because I don't know how to delete
polygons. Any ideas how to do this?
Thanks in advance.
Noli
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--
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.biv...@nhh.no
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