Modifying a column in a Shapefile
Dear Roger,
thank you very much for your help, (and thank you to others who have helped me to set this up)?. The code below seems to convert the data in column NEAR_ANGLE correctly and also writes a new shapefile,although I may have made mistakes that I am not yet aware of.
MergedCentroids <- readOGR("Centroids_Merge.shp","Centroids_Merge")
MergedCentroids$NEARANG_R <- ifelse(MergedCentroids$NEAR_ANGLE<0,MergedCentroids$NEAR_ANGLE+360, MergedCentroids$NEAR_ANGLE)
MergedCentroids$NEARANG_R=90-MergedCentroids$NEARANG_R
MergedCentroids$NEARANG_R <- ifelse(MergedCentroids$NEARANG_R<0,MergedCentroids$NEARANG_R+360, MergedCentroids$NEARANG_R)
write.pointShape(coordinates(MergedCentroids),data.frame(MergedCentroids),paste("NEWMC"))
NEWMCSPDF=readOGR("NEWMC.shp","NEWMC")
However:
#writeOGR(MergedCentroids, "NEWMCSPDF", driver="ESRI Shapefile")
did not work. I will try and find out more about it.
Regards,
Juliane
Below is an example of my data.
coordinates????????????????????? Id PolyFID?? UTMX??? UTMY
?(330430, 3043940)? ??? ??? 0? 187416 330430 3043937???????
?(330430, 3044040)? ??? ??? 0? 187417 330430 3044037???????
?(330430, 3044140)? ??? ??? 0? 187418 330430 3044137???????
?(330430, 3044240)? ??? ??? 0? 187419 330430 3044237???????
(330430, 3044340)?????????????0? 187420 330430 3044337?????
(330430, 3044440)????????????0? 187421 330430 3044437???????
(330430, 3044540)? ??? ??? ??? 0? 187422 330430 3044537???????
?(330430, 3044640)? ??? ??? ??? 0? 187423 330430 3044637???????
?(330430, 3044740)? ??? ??? ??? 0? 187424 330430 3044737???????
?(330430, 3044840)? ??? ??? ??? 0? 187425 330430 3044837???????
?(330430, 3044940)? ??? ??? ??? 0? 187426 330430 3044937???????
?
??? CELLTYPE NEAR_FID NEAR_DIST?? NEAR_X? NEAR_Y NEAR_ANGLE NEARANG_R
500??????? 1????????? ??? 604 ??? ??? 266.91098 330681.3 3043847? -19.66356? ??? ??? ??? ??? 109.6636???
501??????? 1????? ??? ??? 604 ??? ??? 314.96727 330681.3 3043847? -37.05982? ??? ??? ??? ??? 127.0598???
502??????? 1????? ??? ??? 612 ??? ??? 307.32628 330378.1 3044440?? 99.71783? ??? ??? ??? ??? 350.2822???
503??????? 1????? ??? ??? 612 ??? ??? 209.44248 330378.1 3044440? 104.34049? ??? ??? ??? ??? 345.6595???
504??????? 1????? ??? ??? 612 ??? ??? 114.03715 330394.0 3044445? 108.42658? ??? ??? ??? ??? 341.5734???
505??????? 1????? ??? ??? 612?????????19.16420 330423.9 3044455? 108.42658?????????????????????341.5734???
506??????? 1??? ????? ??? 612? ??? ??? 27.46970 330420.8 3044563? 109.47166? ??? ??? ??? ??? 340.5283???
507??????? 1????? ??? ??? 612? ??? ??? 21.19512 330439.2 3044618? -64.29902?????????????????????154.2990???
508??????? 1????? ??? ??? 612???????????111.30209 330478.3 3044637? -64.29902? ??? ??? ??? ??? 154.2990???
509??????? 1????? ??? ??? 612 ??? ??? 201.57582 330516.4 3044655? -64.61209? ??? ??? ??? ??? 154.6121???
510??????? 1????? ??? ??? 612 ??? ??? 291.91840 330555.2 3044673? -64.61209? ??? ??? ??? ??? 154.6121???
?
----- Original Message ----
From: Roger Bivand <Roger.Bivand at nhh.no>
To: Juliane Struve <juliane_struve at yahoo.co.uk>
Cc: r-sig-geo at stat.math.ethz.ch
Sent: Friday, 3 October, 2008 13:33:44
Subject: Re: [R-sig-Geo] Modifying a column in a Shapefile
On Fri, 3 Oct 2008, Juliane Struve wrote:
Dear list members,
I am using a grid called "MergedCentroids" in which I need to
modify?entries in ?column?"NEARANGLE and write the result into a
column?"NEARANG_R". I have tried to convert the Spatial Points Data
Frame to a data frame in order to do this.?I want to convert the updated
grid into a new shapefile at the end. This is my code so far:
MergedCentroids <- readOGR("Centroids_Merge.shp","Centroids_Merge")
write.table(MergedCentroids,file="MergedCentroids.csv",sep=",",row.names=F)
MC=read.csv("MergedCentroids.csv")
MCDF<-as.data.frame(MC)
MCDF$NEARANG_R=ifelse(MCDF$NEARANGLE<0,MCDF$NEARANGLE+360,MCDF$NEARANG)
MCSPDF = SpatialPointsDataFrame(MCDF[,3:4],data.frame(MCDF[,1:16]))
write.pointShape(coordinates(MCSPDF),data.frame(MCSPDF),paste("NEWMCSPDF"))
?
After executing the last statement I get two error messages:
?
write.pointShape(coordinates(MCSPDF),data.frame(MCSPDF),paste("NEWMCSPDF"))
Error in write.dbf(df, paste(file, ".dbf", sep = ""), factor2char = factor2char,? :
? unable to open file
In addition: Warning message:
use writeSpatialShape:
objects other than Spatial objects defined in the sp package are deprecated
?
Would somebody be able to help ?
Difficult to know where to start. If you had used a provided data set, it might have been easier. First, to coerce to a data.frame, use as(), the coerce method: MC <- as(MergedCentroids, "data.frame") What actually got written to the CSV file probably resulted from coercion being invoked internally in write.table() - did you inspect the file? Why not just operate on the MergedCentroids object? MergedCentroids$NEARANG_R <- ifelse(MergedCentroids$NEARANGLE<0, ? MergedCentroids$NEARANGLE+360, MergedCentroids$NEARANG) is quite OK. Why not then simply use: writeOGR(MergedCentroids, "NEWMCSPDF", driver="ESRI Shapefile") I can imagine that the input object is polygons not points, adding one possible extra level, and that the OGR driver does not handle dates gracefully, leading you to prefer writeSpatialShape() in maptools (using the improved write.dbf() in foreign), but not much more reason for the complications you introduce. Simplifying usually helps, as does giving working examples from the included data sets. Roger
? Many thanks ! ? Juliane ?Dr. Juliane Struve Environmental Scientist 10, Lynwood Crescent Sunningdale SL5 0BL 01344 620811
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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.Bivand at nhh.no