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merging several shapefiles into one

5 messages · Nicolas Degallier, Pierre Roudier, Barry Rowlingson +2 more

Original
Nicolas Degallier
# 
Hi All,

I have read different shapefiles that are contiguous and that have different column names with the function "readShapePoly".

example :

noumea <- readShapePoly(noumea.file, IDvar = "NOUMEA2_ID", proj4string = crs_rgnc)

and

dumbea <- readShapePoly(dumbea.file, IDvar = "DUMBEA2_", proj4string = crs_rgnc)

Now I would like to create a new shapefile with all the polygones in the "noumea" and "dumbea" spatial polygone data frames.

I tried :
spRbind(noumea, dumbea)

I get this message error :

Error in spRbind(as(obj, "SpatialPolygons"), as(x, "SpatialPolygons")) :
 non-unique polygon IDs

I have tried with the function rbind()
I have tried to set noumea$NOUMEA2_ID and dumbea$DUMBEA2_ with unique values but I still get the same message error as if the function spRbind was not using those two columns as polygons ID...

Does anyone know how I can fix this problem ?

Thanks a lot

Nicolas


Nicolas Degallier

IRD UMR182
Laboratoire d'Oc?anographie et du Climat, Exp?rimentation et Approches Num?riques (LOCEAN)
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Pierre Roudier
# 
Hi Nicolas,

I do not have a R session handy, but if I remember correctly, the
function gUnion() in the rgeos package would do what you want.

Hope this helps,

Pierre

2011/5/25 Nicolas Degallier <nicolas.degallier at ird.fr>:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Barry Rowlingson
    

    

      
      #
    

  


  

      
On Wed, May 25, 2011 at 8:06 AM, Nicolas Degallier

        
<nicolas.degallier at ird.fr> wrote:

            

      
      
      
    

        
once you've read in your data using NOUMEA2_ID and DUMBEA2_ as the ID
variables, changing the values in the data frame won''t change the ID
attached to each feature.

 You need to use the "spChFIDs-methods" to create new spatial polygons
data frames with unique IDs between them.

 Here, scot1 is the first 10 features from scot_BNG as read in help(rgdal)

 > scot2=scot1
 > scot12=spRbind(scot1,scot2)
 Error in spRbind(as(obj, "SpatialPolygons"), as(x, "SpatialPolygons")) :
  non-unique polygon IDs

 - that fails because the IDs are the same. So we change scot2 to be
"A" to "J" (which isnt what the IDs are currently...)

 > scot2=spChFIDs(scot2,letters[1:10])
 > scot12=spRbind(scot1,scot2)

and that works.

Barry

  
  


  


      

    

    

      
      

        


  

        

      Zia Ahmed
    

    

      
      #
    

  


  

      
I used following code to merge a series of  shape files with similar 
file structure. We can try this, but you need to do some modification of 
the code.
Zia

###############################################################################

# Require packages: rgdal and maptool
#-------------------------------------

library(rgdal)
library(maptools)

# Get list of all shape files from county directories/sptial/
#------------------------------------------------------------

files <- list.files(pattern="soilmu_a_ia.*.shp$", 
recursive=TRUE,full.names=TRUE)
uid<-1

# Get polygons from first file (_001)
#-------------------------------------

poly.data<- readOGR(files[1],gsub("^.*/(.*).shp$", "\\1", files[1]))
n <- length(slot(poly.data, "polygons"))
poly.data <- spChFIDs(poly.data, as.character(uid:(uid+n-1)))
uid <- uid + n

# mapunit polygoan: combin remaining  polygons with first polygoan
#-----------------------------------------------------------------

for (i in 2:length(files)) {
     temp.data <- readOGR(files[i], gsub("^.*/(.*).shp$", "\\1",files[i]))
     n <- length(slot(temp.data, "polygons"))
     temp.data <- spChFIDs(temp.data, as.character(uid:(uid+n-1)))
     uid <- uid + n
     poly.data <- spRbind(poly.data,temp.data)
}

names(poly.data)
proj4string(poly.data)

        
On 5/25/2011 3:22 AM, Pierre Roudier wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        
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