[scilab-Users] Using functions in Java
Sattiraju Prabhakar
maitreyakara at yahoo.com
Fri Jun 19 01:18:24 CEST 2009
Thanks Sylvestre, it is very helpful!
Prabhakar
> -----Original Message-----
> From: Sylvestre Ledru [mailto:sylvestre.ledru at scilab.org]
> Sent: Tuesday, June 16, 2009 12:35 AM
> To: Sattiraju Prabhakar
> Cc: users at lists.scilab.org
> Subject: RE: [scilab-Users] Using functions in Java
>
> Le lundi 15 juin 2009 à 21:34 -0700, Sattiraju Prabhakar a écrit :
> > Thanks Sylvestre! Your response is very helpful.
> Good
>
> > Sorry for the delayed reply.
> No worries
>
> > First, let me explain why I was trying to create Java methods for
> > Scilab functions, without using Scilab.ExecuteScilabScript(String
> filename).
> > I have been developing a complex Java application, and a lot of effort
> > has gone into structuring the application to make it extensible and
> > readable. I would like Java to continue to provide that structure
> while
> > using other programs like Scilab. For example, I can have variations
> of
> > methods as the classes get extended.
> >
> > I agree with you that using Scilab.ExecuteScilabScript(String
> filename)
> > saves time.
> >
> > I tested your suggestion for "Problem Using Function" below -include
> "end".
> > It is still giving error. When I tried to step through the function
> > declaration, in debugger, I found something interesting.
> > Everytime Scilab.Exec() encountered, it returns "false",
> > except in the case of "disp". I think Scilab.Exec requires an
> > executable statements as arguments.
> Yep, it is what I tried to say in my previous email.
>
> > Since the function declaration does not provide statements for
> immediate execution, it returns false
> > (error, according to Scialb.Exec()). I think that is also the
> > reason why it executes disp statement during the function declaration.
> > Am I correct? Is there a way around this problem, without entering the
> function
> > body as a very long string?
> It is not really a problem. Each instruction has to be syntactically
> correct...
> If you do want to be able to do that, you can inherent from the Scilab
> class and create a SQL-commit like feature.
> Ie, write into a buffer your series of commands and once you are happy,
> you commit it (and the commit with just merge all the strings into one
> or write into a temp file and Scilab.ExecuteScilabScript it).
> Am I clear ?
>
>
> > Thanks for suggesting me to include "end". The "string" type solution
> which you provided
> > is working for me too.
> Good.
> > I guess the same problems are applicable to "deff" also.
> Probably !
>
> Sylvestre
>
> > Thanks!
> >
> > Prabhakar
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: Sylvestre Ledru [mailto:sylvestre.ledru at scilab.org]
> > > Sent: Wednesday, June 10, 2009 8:47 AM
> > > To: users at lists.scilab.org
> > > Cc: Sattiraju Prabhakar
> > > Subject: Re: [scilab-Users] Using functions in Java
> > >
> > > Hello,
> > >
> > >
> > > Le samedi 30 mai 2009 à 01:15 -0700, Sattiraju Prabhakar a écrit :
> > > > Hi,
> > > >
> > > > I am trying to use Scilab (5.1.1) from a Java (jdk 6 update 13)
> > > > application.
> > > > I have been experimenting with some Scilab scripts that use
> > > > function ("function" and "deff") definitions.
> > > > When I tried to convert these scripts into Java, I have come
> > > > across a number of problems.
> > > >
> > > > Problems using "function"
> > > > ================
> > > >
> > > > I took the "function percentile" declaration from Professor
> Gilberto
> > > > Gurroz's
> > > > Basic Statistics and Probability using Scilab. I reproduce below
> the
> > > > script.
> > > >
> > > > function [p] = percentile(x,r)
> > > > //This function calculates the 100*r-th percentile
> > > > //(0<r<1) for the vector x
> > > > xx = gsort(x);
> > > > [n m] = size(xx);
> > > > if m>n & n == 1
> > > > n = m;
> > > > end
> > > > if r<0 | r>1 then
> > > > disp('Percentile value must be between 0 and 1');
> > > > else
> > > > k = n*r;
> > > > if k-floor(k) ~= 0
> > > > p = xx(round(n*r));
> > > > else
> > > > p = (xx(k)+xx(k+1))/2;
> > > > end
> > > > end
> > > >
> > > > It is used as follows
> > > > Q1 = percentile(x,0.25)
> > > >
> > > > I tried to put it in Java code in two different ways.
> > > >
> > > > A. In the first attempt, I tried to execute each line using
> > > > Scilab.Exec. The code follows.
> > > >
> > > > public void percentile() {
> > > > Scilab.Exec("function [p] = percentile(x,r)");
> > > > //This function calculates the 100*r-th percentile
> > > > //(0<r<1) for the vector x
> > > > Scilab.Exec("xx = gsort(x);");
> > > > Scilab.Exec("[n m] = size(xx);");
> > > > Scilab.Exec("if m>n & n == 1");
> > > > Scilab.Exec("n = m;");
> > > > Scilab.Exec("end");
> > > > Scilab.Exec("if r<0 | r>1 then");
> > > > Scilab.Exec("disp('Percentile value must be between 0 and
> > > > 1');");
> > > > Scilab.Exec("else");
> > > > Scilab.Exec("k = n*r;");
> > > > Scilab.Exec(" if k-floor(k) ~= 0");
> > > > Scilab.Exec("p = xx(round(n*r)); ");
> > > > Scilab.Exec("else");
> > > > Scilab.Exec("p = (xx(k)+xx(k+1))/2;");
> > > > Scilab.Exec("end");
> > > > Scilab.Exec("endfunction");
> > > > }
> > > Why don't you directly store this into a dedicated percentile.sci
> file
> > > and call the java method Scilab.ExecuteScilabScript(String filename)
> ?
> > >
> > > Btw, your error is due to a missing end just before the endfunction.
> > >
> > >
> > > > I tried to apply this function as follows.
> > > > SciDouble Q1P = new SciDouble("Q1");
> > > > Scilab.Exec("Q1 = percentile(x,0.25)");
> > > > Q1P.Get();
> > > > Q1P.disp();
> > > >
> > > > I get the following error.
> > > > double Q1=
> > > >
> > > > 0.
> > > > Error in Java_javasci_Scilab_Exec routine.
> > > This is normal that it is failling here.
> > > Scilab.Exec is waiting for a consistent expression.
> > >
> > > If you try:
> > > if (!Scilab.Exec("function [p] = percentile(x,r)")){
> > > System.out.println(Scilab.GetLastErrorCode());
> > > }
> > > you will that that you will get an error (code 272... no
> endfunction).
> > >
> > >
> > > > B. I tried to declare the entire function as a string and pass the
> > > > string as argument to Scilab.Exec().
> > > >
> > > >
> > > > public void percentile() {
> > > > String perc2 = "function [p] = percentile(x,r) \n xx =
> gsort(x);
> > > > \n [n m] = size(xx); \n if m>n & n == 1 \n n = m; \n end \n if r<0
> |
> > > > r>1 then \n disp('Percentile value must be between 0 and 1'); \n
> else
> > > > \n k = n*r; \n if k-floor(k) ~= 0 \n p = xx(round(n*r)); \n else
> \n p
> > > > = (xx(k)+xx(k+1))/2; \n end \n endfunction";
> > > > Scilab.Exec(perc2);
> > > > }
> > >
> > > > I tried it without \n, and later with \n. In both cases, I got the
> > > > same error as above.
> > > Same issue, you forgot the end.
> > >
> > > The following code is working for me:
> > > import javasci.*;
> > > public class percentile {
> > >
> > >
> > > public static void main(String args[]){
> > > String aze="function [p] = percentile(x,r); xx = gsort(x);
> > > [n m] =
> > > size(xx); if m>n & n == 1 n = m; end; if
> r<0
> > > | r>1 then disp('Percentile value must be between 0 and 1');
> > > else; k = n*r; if k-floor(k) ~= 0; p =
> > > xx(round(n*r)); else; p = (xx(k)+xx(k+1))/2;
> end;
> > > end; endfunction";
> > > if (!Scilab.Exec(aze)){
> > > System.out.println(Scilab.GetLastErrorCode());
> > > }
> > > SciDouble Q1P = new SciDouble("Q1");
> > > Scilab.Exec("x=[23,2323,934,42];");
> > > Scilab.Exec("Q1 = percentile(x,0.25)");
> > > Q1P.Get();
> > > Q1P.disp();
> > > }
> > > }
> > >
> > > > 2. Using deff
> > > > =============
> > > >
> > > > I was able to successfully write and execute the above example
> using
> > > deff
> > > >
> > > > Scilab.Exec("deff('[x,y]=myfct(a,b)', ['x=a+b'; 'y=a-b'])");
> > > >
> > > > "deff" requires that we state the "statements" of the function as
> > > matrix of strings.
> > > > If you have a String inside the function declaration (of Scilab
> > > script), as in percentile, then
> > > > it becomes a problem.
> > > >
> > > > I was not able to get a correct result for percentile using deff
> and
> > > Java.
> > > > Here is my code:
> > > > Scilab.Exec("deff('[p]=percentile(x,r)', ['xx = gsort(x);'; '[n m]
> =
> > > size(xx);'; ' if m>n & n == 1 n = m;'; 'end'; 'if r<0 | r>1 then
> > > disp('Percentile value must be between 0 and 1');' ; 'else k =
> n*r;';
> > > 'if k-floor(k) ~= 0 p = xx(round(n*r));'; 'else p =
> > > (xx(k)+xx(k+1))/2;'; 'end' ])");
> > > Probably the same issue as before.
> > >
> > > > I would like to end with a general question. Each of the above
> methods
> > > > takes some effort.
> > > > If the function definition is long, then the effort needed to
> convert
> > > > into Java code can be
> > > > substantial. Is there a simple method?
> > > Yep, load the function from a file.
> > >
> > > Sylvestre
> >
> >
> >
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