[R-sig-Geo] read in a csv with readOGR

[Roger Bivand]

On Thu, 1 Apr 2010, Barry Rowlingson wrote:

> On Thu, Apr 1, 2010 at 10:19 PM, James Stegen <stegen at email.unc.edu> wrote:
>> I am trying to read-in a .csv file that has two columns, one for longitude
>> and one for latitude to then overlay on a raster map that I am reading in
>> with readGDAL.
>> I read in the raster as:
>>
>> test = readGDAL("tmean1.bil")
>>
>> This seems to work fine.
>> I then try to read in the csv file as:
>>
>> coord = readOGR("Lat_Long_105.csv",layer="Lat_Long_105")
>>
>> , but I get this out
>>
>> Error in ogrInfo(dsn = dsn, layer = layer, input_field_name_encoding =
>> input_field_name_encoding) :
>>  Multiple # dimensions:
>>
>> It's unclear to me if I am totally missing the boat when I try to read in
>> the csv file. In particular, dsn is also the layer (i.e. there is only one
>> file).
>> Do I need something else for the layer?
>
> Read it into a non-spatial, ordinary, common-or-garden dataframe with
> 'read.csv'. Then give it coordinates, something like:

While this is the standard answer, you can also create a *.vrt file to 
accompany your csv file, as described in:

http://www.gdal.org/ogr/drv_csv.html

For larger projects, this means that the OGR driver will read the data 
successfully. With just the *.csv file, however, go though read.csv() or 
read.csv2(); in some cases in some locales, read.csv2() may be the only 
option, as explained on the CSV driver help page.

Roger

>
> thing = read.csv("thing.csv")
> coordinates(thing)=~long+lat
>
> then by magic you'll have a spatial points data frame
>
> that's assuming your column names in 'thing' are long and lat for X
> and Y coords. You might also want to set a CRS too, so it knows what
> coordinate system it is (probably WGS 84...)
>
> Barry
>
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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