Using SJava?

Frank and Roger,

Sorry about the path reference - I just added the example on the fly in the
email and forgot about the R escape character.  Attached is the simply class
that I used to test the link.  It just takes a string as an input and
returns my email signature with the string substituted for the name.

The R code to run it:

library(SJava)
.JavaInit(config=javaConfig(classPath="F:/_ben/java"))
.Java("sig","print","Ben Stabler")


In terms of the jar file, it seems to work for me.  Note that I moved the
jar file to a different directory so it did not find the class file by
itself as well.

library(SJava)

using JAVA_HOME = C:\j2sdk1.4.2\jre 

.JavaInit(config=javaConfig(classPath="F:/_ben/sig.jar"))
.Java("sig","print","Ben Stabler")

[1] "Ben Stabler"                         "Oregon Department of
Transportation"
[3] "Mill Creek Office Building"          "555 13th Street NE Suite 2"

[5] "Salem, OR 97301-4178"               

The print method of the sig class is static so I'm not having any difficulty
using static methods and I did not need to create a constructor first.  You
shouldn't need a constructor/object for a static method (that is the point
of static methods).  Unfortunately my IS department blocked the zip file you
sent.  Could you send me the code as text or maybe just copy into email?
Thanks.  

Ben

-----Original Message-----
From: Frank Hardisty [mailto:HardistF at gwm.sc.edu]
Sent: Monday, April 05, 2004 1:07 PM
To: Roger.Bivand at nhh.no
Cc: STABLER Benjamin
Subject: Re: [R-sig-Geo] RE: Using SJava?


Roger and Benjamin,

Benjamin, your advice is good and the test class does work. Roger, one
difficulty is that we were calling a static method of the class, which
does NOT work for some reason. However, the class can be instantiated
and used from within R. Here's my session with my mistakes edited out:

[Previously saved workspace restored]

library(SJava)

using JAVA_HOME = C:\programs\j2sdk_nb\j2sdk1.4.2 

.JavaInit(config=javaConfig(classPath="C:/temp/javatest/test.jar"))
testClass <- .JavaConstructor("TestJava")
.Java(testClass,"getMessage")

[1] "Hi Roger!"

Benjamin, do you also find that static methods don't work in SJava?
It's hard to understand, because calls to static methods in the Java
runtime libraries work just fine, for example, 

.Java("Math","random")

[1] 0.07714792

regards,
-Frank

Roger Bivand <Roger.Bivand at nhh.no> 04/05/04 03:36PM >>>

On Mon, 5 Apr 2004 Benjamin.STABLER at odot.state.or.us wrote:

Hopefully, I'm not too late on this one....when you initialize the

JVM you

need to set the class path as follows:

.JavaInit(config=javaConfig(classPath="StringDirectoryPathReference"))

or

.JavaInit(config=javaConfig(classPath=c("String1", "String2")))

for example:

.JavaInit(config=javaConfig(classPath="C:\javastuff"))

where javastuff contains my class files.  You need to specify the jar

file

name if you are trying to include class files within jars.  I have

used it

with some classes that I wrote.  

Yes, and Sys.putenv("CLASSPATH"="String1") can be used too, but what do

you put in .Java() to get into your own jars? Are there escaping issues
in 
the path to the jars? (backslash twice? forwardslash?) Could we put up

some jars and some instructions for use on a website? Frank Hardisty
sent 
me an example off-list that works from the command line but which I
can't 
find from within R/SJava (Windows XP, the SJava examples that I've
tried 
work for me). 

The idea would be to see if GeoTools2 can be reached from within R, 
because it could provide (another) way to import/export multiple GIS 
formats.

Roger

I too am excited about linking Java and R, as there is so much useful

code

in the Java community.

Benjamin Stabler
Transportation Planning Analysis Unit
Oregon Department of Transportation
555 13th Street NE, Suite 2
Salem, OR 97301  Ph: 503-986-4104

Message: 5
Date: Fri, 2 Apr 2004 20:56:50 +0200 (CEST)
From: Roger Bivand <Roger.Bivand at nhh.no>
Subject: [R-sig-Geo] Using SJava?
To: r-sig-geo at stat.math.ethz.ch 
Cc: Frank Hardisty <HardistF at gwm.sc.edu>
Message-ID:

<Pine.LNX.4.44.0404022042580.28093-100000 at reclus.nhh.no>

Content-Type: TEXT/PLAIN;	charset=US-ASCII

Is anyone on this list using SJava or any R/Java connection? 
Not only is
the JTS Topology Suite that Tim just mentioned interesting, 
but so is the
upcoming GeoTools2 at http://www.geotools.org/. Both are 
likely to be used 
quite a lot, and thus probably well-maintained.

At the recent Association of American Geographers meeting, 
Frank Hardisty
asked me about this, and while I was able to install SJava (from
http://www.stats.ox.ac.uk/pub/RWin) on a Win XP laptop, we 
were not able
to see how to get Java within R to see GeoTools in its 
classpath.  Both of
these Java resources are potentially useful, and R opinions 
two or three
years ago, that Java is slow, may need revision given increased

machine

capacity. I feel we could benefit from mobilizing Java insight 
(but I feel
personally Java-challenged!).

I believe that Duncan Temple-Lang was playing with/working on object

discovery - this could be very relevant in terms of matching 
R-internal 
object representations with those in existing software that we 
could - if 
SJava worked - link to. I also think that we could ask him for 
advice if 
we discussed it first here. What do others think?

-- 
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 

-- 
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