[R] data format for ppinit

[Roger Bivand]

On Mon, 10 Sep 2001, Susumu [ISO-2022-JP] Tanimura/$BC+B<(B $B?8(B wrote:

> After installation of R into VineLinux2.1.5, I started to enjoy statistics
> following some instruction, and found it very useful.
> 
> One of my main purpose to use R is to try spatial statistics.  Since
> library named "spatial" has already installed, I just tried ...
> > library(spatial)
> > towns <- ppinit(test.dat)

help(ppinit)

gives the documentation for ppinit. If you look at:

example(ppinit)

and examine the file it reads ($R_HOME/library/spatial/data/towns.dat),
you will see that the format described on the help page is easy to 
follow:

69
TOWNS
0 40 0 40 1
  .84 39.16
  .84 33.20
 4.24 34.04
....

69 points
a header
xl xu yl yu scale (the point (xl, yl) is the lower left corner of the
region of interest, (xu, yu) the upper right corner; scale is usually 1)
followed by coordinate pairs for the specified number of points.


> ------- test.dat -------
> x,y
> 4,7
> 5,7
> 5,8
> 5,9
> 6,7
> 6,8
> 6,9
> 7,8
> 
> --------------------------

This is a different problem. You are assuming that you can use commas to
separate values - in general values should be separated by white
space. For ppinit, your file would need to be:

8
TEST
3 8 6 10 1
4 7
5 7
5 8
5 9
6 7
6 8
6 9
7 8

> pptest <- ppinit("/tmp/test.dat")
> str(pptest)
List of 3
 $ x   : num [1:8] 4 5 5 5 6 6 6 7
 $ y   : num [1:8] 7 7 8 9 7 8 9 8
 $ area: Named num [1:4] 3 8 6 10
  ..- attr(*, "names")= chr [1:4] "xl" "xu" "yl" "yu"
> plot(pptest)

now works fine. Please also refer to the section of Venables & Ripley
(Modern Applied Statistics with S-Plus) about the functions provided in
the spatial package.

Roger

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no
and: Department of Geography and Regional Development, University of
Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland.

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