[R-sig-Geo] Shows error when I try to write shape file-Re: Combing attribute table with polygon??

[Robert J. Hijmans]

Here is reproducible example, #1 fails because what I suspect is a bug
in merge, but #2 works. Robert

 library(maptools)
 data(wrld_simpl)
# create some data to merge with
 m = sort(unique(wrld_simpl at data$REGION))
 m = cbind(m, 1:length(m))
 colnames(m) = c('REGION', 'v')
# merge
 wrld_simpl at data = merge(wrld_simpl at data, m, by='REGION', all.x=TRUE,
sort=FALSE)

# but this does not work:
col = terrain.colors(nrow(m))
plot(wrld_simpl, col=col[wrld_simpl$v])
# he data.frame is rearanged; despite "sort=FALSE"
# this looks like a bug in merge to me. Anyone, am I wrong?


Therefore, I would do

library(maptools)
data(wrld_simpl)
# get the data.frame out of the SPGDF; to simplify code
d = wrld_simpl at data
# add a sort key
d$sort = 1:nrow(d)
# create some data to merge with
 m = sort(unique(d$REGION))
 m = cbind(m, 1:length(m))
 colnames(m) = c('REGION', 'v')
# merge
 x = merge(d, m, by='REGION', all.x=TRUE)
# sort
 x = x[order(x$sort),]
# put the data back
 wrld_simpl at data = x


# now it works
col = terrain.colors(nrow(m))
plot(wrld_simpl, col=col[wrld_simpl$v])


On Wed, Jan 27, 2010 at 6:59 PM, Zia Ahmed <zua3 at cornell.edu> wrote:
> Hi, Roberts,
> In my last mail, I mentioned it works fine,  but when I try write shape file
> after merging it shows error. I think I need to  define  spatial object or
> data frame after merging. I do not know  how to do this. Thanks again.
> Zia
>
>> poly.data1 = merge(poly.data, data.table, by="MUKEY" ,all.x = TRUE)
>> names(poly.data1) # polygoan
> [1] "MUKEY"      "AREASYMBOL" "SPATIALVER" "MUSYM"      "Sand"     [6]
> "Silt"       "Clay"       "pH"         "CEC"        "EC"       [11] "SAR"
>      "CaCO3"      "SOM"        "BD"         "AWC"      [16] "KSAT"
> "Kf"         "Kw"         "LL"         "LEP"
>>polyShp <- "D:/test/mapunit_poly.shp" > writeOGR(poly.data1, dsn=polyShp,
>> layer="mapunit_poly", driver="ESRI Shapefile")
> Error in writeOGR(poly.data1, dsn = polyShp, layer = "mapunit_poly", driver
> = "ESRI Shapefile") :
>  obj of wrong class
>
> Zia Ahmed wrote:
>>
>> Thank you so much Roberts! it works.
>>
>> Zia
>>
>> Robert J. Hijmans wrote:
>>>
>>> Zia, something like this might work as long as MUKEY has no NA values:
>>>
>>> poly.data = merge(poly.data, data.table, by="MUKEY" ,all.x = TRUE)
>>>
>>> Robert
>>>
>>> On Wed, Jan 27, 2010 at 1:58 PM, Zia Ahmed <zua3 at cornell.edu> wrote:
>>>
>>>>
>>>> I have created one data table and one polygon in R. Both have a similar
>>>> type
>>>> of column.  I want to combine or join them with this column or field
>>>> ("MUKEY").  Then  I will convert this polygon  as  a ESRI  shape file.
>>>> But  when  I  used  spCbind,   I got error. I think i miss something
>>>> here.
>>>> Is there any way join attribute table with polygon? Thanks
>>>> Zia
>>>>
>>>> poly.data1 <- spCbind(poly.data, data.table)
>>>> Error in spCbind(poly.data, data.table) : different numbers of rows
>>>>
>>>>
>>>> names(poly.data) # polygoan
>>>> [1] "AREASYMBOL" "SPATIALVER" "MUSYM"      "MUKEY"    >
>>>> names(data.table) #
>>>> data
>>>> [1] "MUKEY" "Sand"  "Silt"  "Clay"  "pH"    "CEC"   "EC"    "SAR"
>>>> "CaCO3"
>>>> [10] "SOM"   "BD"    "AWC"   "KSAT"  "Kf"    "Kw"    "LL"    "LEP"
>>>>
>>>>>
>>>>> length(poly.data$MUKEY)
>>>>>
>>>>
>>>> [1] 76969
>>>>
>>>>>
>>>>> length(data.table$MUKEY)
>>>>>
>>>>
>>>> [1] 184
>>>>    poly.data1 <- spCbind(poly.data, data.table)
>>>>
>>>> combinedShp1 <- "D:/test/combined1.shp" writeOGR(poly.data1,
>>>> dsn=combinedShp1, layer="combined1", driver="ESRI Shapefile")
>>>>
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>>>>
>>>>
>>
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