[R-sig-Geo] Importing only lines from big shape file

[Roger Bivand]

On Thu, 24 Apr 2014, Agus Camacho wrote:

> Thanks for the fast response,
>
> @ Barry
> The .shp file is 420,241KB, the .shx is 6,994KB and the .dbf is 1,729,941KB.
> @ Javier, id like to use the whole region.

But you'll never be able to render the detail in this coastline anyway. 
Why not just use maptools::Rgshhs with the intermediate binary dataset, 
setting a sensible bounding box? I've had trouble with the newest fine 
data set and with the equivalent 2.3.0 shapefile (missing Norwegian 
islands), but an older version (2.1.0) was fine.

Roger


>
> Might be any easy way to reduce the number of vertex previously to import?
>
> These shape files are available at:
> http://mapas.mma.gov.br/mapas/aplic/probio/datadownload.htm
>
>
>
>
>
>
>
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> 2014-04-24 13:02 GMT-03:00 Javier Garcia-Pintado <
> j.garcia-pintado at reading.ac.uk>:
>
>> A possibility is, if you are interested in some specific area of the mata
>> atlantica, to crop the file externally with OGR just for your study area,
>> and read the cropped file into R.
>>
>> Javier
>> ---
>> __________
>> From: r-sig-geo-bounces at r-project.org [r-sig-geo-bounces at r-project.org]
>> on behalf of Barry Rowlingson [b.rowlingson at lancaster.ac.uk]
>> Sent: 24 April 2014 16:58
>> To: Agus Camacho
>> Cc: r-sig-geo
>> Subject: Re: [R-sig-Geo] Importing only lines from big shape file
>>
>> On Thu, Apr 24, 2014 at 4:47 PM, Agus Camacho <agus.camacho at gmail.com
>>> wrote:
>>
>>> Dear Rgeos,
>>>
>>> Id like to know if there is some workaround to import  the lines
>> contained
>>> by a shape file, avoiding memory problems when the only thing you need is
>>> the lines it contains.
>>>
>>> I mean, reading the lines of the world's coast lines can be done in a
>>> instant with:
>>>
>>> wcoastline <- PBSmapping::importShapefile("GSHHS_c_L1.shp")#
>>>
>>> However, reading a relatively small region, like the brazilian atlantic
>>> forest, seems impossible for my little laptop.  I tried all of these
>>> possibilities.
>>>
>>> AF=PBSmapping::importShapefile("mata_atlantica.shp")
>>> AF=rgdal::readOGR("dir",layer="mata_atlantica")
>>> AF=shapefiles::read.shp("mata_atlantica.shp")
>>>
>>> Any hint would be very welcome.
>>>
>>
>>  Ummm not sure this makes sense. You can read all the coastlines, but not
>> some of the coastlines?
>>
>>  Are the mata_atlantica  files bigger because they are more detailed?
>> Sometimes global data is generalized.
>>
>>  Show us the size in bytes of the files...
>>
>> Barry
>>
>>         [[alternative HTML version deleted]]
>>
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>
>
>
>

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 91 00
e-mail: Roger.Bivand at nhh.no