Merging shapefiles and csv

I am not sure about the mismatch issue, but I thinking merging the
data slot of spatialPolygonsDataFrame with a data frame produces
undesirable results.

I wrote a function a while back that does the merge in such a way that
the problems are avoided, and perhaps this might help.  I think there
are other, more recent, and undoubtedly better solutions (in fact I
recall seeing a very recent thread about this, but not sure where)
than this one that you could find.

joinAttributeTable <- function(x, y, xcol, ycol) {
# Merges data frame to SpatialPolygonsDataFrame, keeping the correct
order. Code from suggestions at:
# https://stat.ethz.ch/pipermail/r-sig-geo/2008-January/003064.html
# Args:
#   x: SpatialPolygonsDataFrame
#   y: Name of data.frame to merge
#   xcol: Merge column name
#   ycol: Merge column name
# Returns: Shapefile with merged attribute table

   x$sort_id <- 1:nrow(as(x, "data.frame"))  # Column containing
original row order for later sorting

   x.dat <- as(x, "data.frame")  # Create new data.frame object
   x.dat2 <- merge(x.dat, y, by.x = xcol, by.y = ycol)  # Merge
   x.dat2.ord <- x.dat2[order(x.dat2$sort_id), ]  # Reorder back to original
   x2 <- x[x$sort_id %in% x.dat2$sort_id, ]  # Make new set of
polygons, dropping those which aren't in merge
   x2.dat <- as(x2, "data.frame")  # Make update x2 into a data.frame
   row.names(x.dat2.ord) <- row.names(x2.dat)  # Reassign row.names
from original data.frame
   x2 at data <- x.dat2.ord  # Assign to shapefile the new data.frame
   return(x2)
}

Hope it helps.

Best, Lyndon


On Thu, Jul 31, 2014 at 8:32 AM, HallS <sam_l_cruickshank at hotmail.com> wrote:

Hi all,

I'm struggling to know how this will come across as my data is confidential.

Basically I have a shapefile (.shp) and a csv file while contain the same
regions (i.e.) a column which has the same information.  Using this link:
https://sites.google.com/site/eospansite/alobotips/spatial_r_tips/rshp_xls
I managed to get quite far but once I got to the writeOGR command, I get the
error
  Error in writeOGR(RSANHS, dsn = "C:/Users/Laptop/Documents/Rworkspace/",  :
   number of objects mismatch

shape1 at data <- merge(shape1 at data,csv,by.x="RSA",
+                           by.y="RSA", all.x=T, sort=F)

###Checking it
dim(shape at data)

[1] 1745    2

dim(shape1 at data)

[1] 1747    5

This shows a discrepancy in two rows between the original shapefile and the
new merged one.  When I looked at the merged file in full, there were a
number of NA rows at the bottom where there was no corresponding data to the
shapefile.  I tried shape1 at data <- na.exclude(shape1 at data) and with na.omit,
and this did reduce the number of rows to 1690, but the problem persists.

Sorry if this is a really unhelpful question, I'm not sure how to do it when
data is confidential.



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