[GRASS-stats] Loading a point-vector table with 466 columns

[Roger Bivand]

On Sat, 23 May 2009, Nikos Alexandris wrote:

> Just FYI
>
> # almost an hour...
> Sys.time() ; sample_2 <- readVECT6("sample_2_grid_points") ; Sys.time()
> [1] "2009-05-22 23:25:02 CEST"
> OGR data source with driver: GRASS
> Source:
> "/geo/grassdb/peloponnese/evaluation_utm/nik/vector/sample_2_grid_points/head", layer: "1"
> with  875  rows and  466  columns
>
> Feature type: wkbPoint with 3 dimensions
> [1] "2009-05-23 00:22:12 CEST"

Thanks, this is helpful. As you can see, the work is being done by the OGR 
GRASS driver, not by writing a shapefile with v.out.ogr and reading that 
shapefile with the shapefile driver in OGR. Since these are just points, 
the simplest geometry, something is making the driver run slowly.

Does plugin=FALSE speed it up or slow it down (that would force the use of 
a temporary shapefile)?

Does anyone know of interactions between SQLite storage and the OGR GRASS 
driver?

By the way, just put the command inside system.time() to time it.

>
>
> # while reading the csv...
>> Sys.time() ; sample_2 <-
> read.csv(file="sample_2_grid_points_table.csv") ; Sys.time()
> [1] "2009-05-23 01:39:51 CEST"
> [1] "2009-05-23 01:39:52 CEST"
>

This is not a fair comparison, because you have to dump the CSV file from 
the GRASS database first, although it won't take long. What are you using 
to do that? Have you considered connecting to the SQLite file directly 
from R? Are the (2) coordinates present in the table? See:

http://cran.r-project.org/web/packages/RSQLite/index.html

for direct reading.

Roger

>
> Kindest regards, Nikos
>
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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