[Rd] Fetching Warning Messages

[Nikhil Shah]

Hi,

    I read the help page and saw that warnings() actually prints the warning
message and stores warning in top-level variable "last.warning". So it seems
that it is almost impossible to access last warning from java code. I got
another solution of fetching warning messages by storing warning messages in
a file and reading the file later. This can be done by using sink() command,
but before that options(warn=1) must be set.

> Please read the help page on options("warn") and see what warnings()
> does. (I am pretty sure you have asked this and been told before.)
>
> There should not be an object called last.warning in your example.
>

    I read help page

> On Mon, 22 Aug 2005, Nikhil Shah wrote:
>
> > Hi,
> >
> >    I am facing one problem of fetching R warning messages in Java Code
> > using Rserve. It is easier to trap R Error messages by using catching
> > RSrvException. I came to know one way of fetching R Warning messages,
i.e.
> > using "withCallingHandlers", below is my Java Program, which uses
> > withCallingHandlers of R :
> > import org.rosuda.JRclient.*;
> >
> > ---------------------------RWarning.java-----------------------
> > class RWarning
> > {
> >   public static void main(String args[])
> >  {
> >     try
> >     {
> >       String hostName = null;
> >       hostName = args[0];
> >       Rconnection c = new Rconnection(hostName);
> >       c.voidEval("lastWarning <- NULL");
> >       c.voidEval("withCallingHandlers(
> > {x<-sqrt(-9);y<-matrix(1:9,ncol=4);z<-sqrt(4)} , warning = function (w)
{
> > lastWarning <<- paste(lastWarning,as.character(w))})"); //This will
generate
> > warning message[sqrt(-9)], another warning message [
matrix(1:9,ncol=4) ]
> > and successful completion [ sqrt(4) ]
> >        System.out.println(c.eval("z").asDouble());
> >        System.out.println(c.eval("lastWarning").asString());
> >        c.close();
> >        System.out.println("DONE");
> >      }
> >      catch(RSrvException  e)
> >      {
> >         System.out.println("Error : " + e.getMessage());
> >         e.printStackTrace();
> >      }
> >   }
> > }
> > ---------------------------End Of RWarning.java-----------------------
> >
> > Output of above program is (as expected) :
> >
> > 2.0
> > simpleWarning in sqrt(-9): NaNs produced
> > simpleWarning: data length [9] is not a sub-multiple or multiple of the
> > number of columns [4] in matrix
> >
> > DONE
> >
> >
> >
> >     Now my query is that if there is any way of using warnings()
function
> > in Java Program to fetch all warnings. I used it in my program but
returns
> > me NULL instead of warning messages. I also used last.warning but it
Java
> > Program gives an error saying that last.warning object is not found. I
have
> > pasted both the java code below :
> >
> > This is the java program that I have written to use "last.warning"
object of
> > R. Please explain me where the error could be.
> >
> > ------------Code of RWarning1.java----------------
> >
> > import org.rosuda.JRclient.*;
> >
> > class RWarning1
> > {
> >  public static void main(String args[])
> >  {
> >    try
> >    {
> >      String hostName = null;
> >      hostName = args[0];
> >      Rconnection c = new Rconnection(hostName);
> >      System.out.println(c.eval("x<-sqrt(-9)").asString());
> >      System.out.println(c.eval("last.warning").asString());
> >      c.close();
> >      System.out.println("DONE");
> >    }
> >    catch(RSrvException  e)
> >    {
> >      System.out.println("Error : " + e.getMessage());
> >      e.printStackTrace();
> >    }
> >  }
> > }
> > ------------End of code of RWarning1.java------------------
> >
> > output of RWarning1.class
> >
> > null
> > Error : Request return code: 127 [request status: Error (127)]
> > org.rosuda.JRclient.RSrvException: Request return code: 127 [request
status:
> > Err
> > or (127)]
> >        at org.rosuda.JRclient.Rconnection.eval(Rconnection.java:190)
> >        at RWarning.main(RWarning.java:13)
> >
> > In other words, when I use "last.warning" in eval method, I simply get
an
> > exception, instead of value of last.warning.
> >
> >
> > Below is the java code of using warnings() function.
> >
> > ------------Code of RWarning2.java----------------
> >
> > import org.rosuda.JRclient.*;
> >
> > class RWarning2
> > {
> >  public static void main(String args[])
> >  {
> >  try
> >  {
> >    String hostName = null;
> >    hostName = args[0];
> >    Rconnection c = new Rconnection(hostName);
> >    System.out.println(c.eval("x<-sqrt(-9)").asString());
> >
> >
System.out.println(c.eval("paste(capture.output(warnings()),collapse='\n')")
> > .asString());
> >    c.close();
> >    System.out.println("DONE");
> >  }
> >  catch(RSrvException  e)
> >  {
> >    System.out.println("Error : " + e.getMessage());
> >    e.printStackTrace();
> >  }
> > }
> > }
> > ------------End of code of RWarning2.java------------------
> > output of RWarning2.class
> >
> > null
> > NULL
> > DONE
> >
> >
> >  Please let me know where I am making mistake.
> >
> > Regards,
> >
> > Nikhil Shah
> >
> > ______________________________________________
> > R-devel at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> >
>
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>

Regards,

Nikhil Shah