[R-sig-Geo] readShapePoly function and putting text on map

[Roger Bivand]

On Thu, 16 Dec 2010, Roger Bivand wrote:

> On Thu, 16 Dec 2010, Wang, Kevin (SYD) wrote:
>
>> Hi all,
>> 
>> I've managed to draw a map using the following code:
>> 	lga1 <- readShapePoly("D:/Documents and Settings/kevinwang/My
>> Documents/SMS/ASGC/LGA10aAust", IDvar = "LGA_CODE10")
>> 	plot(lga1[lga1$STATE_CODE == 7,], border="blue")
>> 	title(main = "NT LGA Division")
>> 	text(coordinates(lga1[lga1$STATE_CODE == 7,]), labels =
>> sapply(slot(lga1[lga1$STATE_CODE == 7,], "polygons"),
>> 
>> function(i) slot(i, "ID")), cex=0.6)
>> 
>> This gives me a map of Northern Territory (Australia), with local
>> government division LGA and the code for the LGAs in each LGA.
>> 
>> However, instead of the LGA code, I'm trying to use LGA names (which is
>> in a variable called LGA_NAME10) instead.  But when I tried to change
>> the IDvar I got:
>> 	> lga1 <- readShapePoly("D:/Documents and Settings/kevinwang/My
>> Documents/SMS/ASGC/LGA10aAust", IDvar = "LGA_NAME10")
>> 	Error in `row.names<-.data.frame`(`*tmp*`, value = c("Albury
>> (C)", "Armidale Dumaresq (A)",  :
>> 	  duplicate 'row.names' are not allowed
>> 	In addition: Warning message:
>> 	non-unique value when setting 'row.names': 'Campbelltown (C)'
>> 
>> My guess is that there are duplicated names in LGA_NAME10 variable.  So
>> I'm wondering if it's possible to specify "LGA_NAME10" in the text()
>> function instead?
>
> Maybe:
>        lga1_7 <- lga1[lga1$STATE_CODE == 7,]
>        plot(lga1_7, border="blue")
>        title(main = "NT LGA Division")
>        text(coordinates(lga1_7),
>            labels = as.character(lga1_7$LGA_NAME10), cex=0.6)
>

Correction, sorry:

> (above you could have said labels=rownames(lga1)[lga1$STATE_CODE == 7], the
                                     ^^^^^^^^
                                     row.names

Roger

> example on the help hasn't been updated, but will be now - thanks for 
> reminding me).
>
> Roger
>
>> 
>> Thanks in advance for the help!
>> 
>> Cheers
>> Kevin
>> 
>> 
>> 
>> Kevin Wang
>> Senior Adviser, Government Advisory Services
>> Advisory
>> 
>> KPMG
>> 10 Shelley Street
>> Sydney  NSW  2000  Australia
>> 
>> Tel 	+61 2 9335 8282
>> Fax	+61 2 9335 7001
>> Mob	0404 518 301
>> kevinwang at kpmg.com.au <mailto:kevinwang at kpmg.com.au >
>> 
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>> 
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>> 
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>> 
>> 
>>
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>> 
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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