[R] Calling R functions in Delphi

[Tom Backer Johnsen]

Earl F. Glynn wrote:
> Thanks for the great example, Tom.
> 
> "Tom Backer Johnsen" <backer at psych.uib.no> wrote in message 
> news:4575AE08.8010304 at psych.uib.no...
>> Anna Belova wrote:
> 
>>> We would like to call quantile() function from the R-package STATS in a
>>> Delphi program. If this is possible, could anyone provide us with an
>>> example?
>> It is possible, and in principle simple.  The essentials:  (1) Write a
>> file containing the something like a script in R with whatever
>> commands. (2) Start a process involving the execution of R with a
>> command line containing two arguments, the name of the command file
>> and the file where you want the output (results) to be. (3) wait for
>> the process to stop.  So, here is a function (returns true if
>> everyhing worked OK) that does that:
> 
> . . .
> 
>>    CreateOK := CreateProcess(Nil, PChar('R.exe ' + CommandLine), nil,
>>       nil,False, CREATE_NEW_PROCESS_GROUP+NORMAL_PRIORITY_CLASS, nil,
>>       nil, StartInfo, proc_info);
> 
> I had to give the full path to the R executable to get this to work:
> 
>    CreateOK := CreateProcess(Nil, PChar('C:\Program 
> Files\R\R-2.4.0\bin\R.exe ' + CommandLine), nil,
>        nil,False, CREATE_NEW_PROCESS_GROUP+NORMAL_PRIORITY_CLASS, nil,
>        nil, StartInfo, proc_info);

That (I think) would depend on whether the directory to the R.exe is 
in the path for the Windows system you use (which I seem to remember I 
added in my environment).  In any case, I was looking for some kind of 
an interface to R late last spring, and this was what I arrived at. 
Which worked.
> 
> I used Delphi 7 to test StartRAndWait with this button press event:
> 
> procedure TForm1.Button1Click(Sender: TObject);
>   VAR
>     Command: STRING;
> begin
>   Screen.Cursor := crHourGlass;
>   TRY
>     Command := 'CMD  BATCH  Sample.R  SampleOutput.txt';
>     StartRAndWait(Command);
>   FINALLY
>     Screen.Cursor := crDefault
>   END
> end;

Looks sensible to me.
> 
> 
> Sample.R file
> =====================
> sink('quantile.txt')
> quantile(0:100)
> sink()
> =====================
> 
> I used sink in the R script to isolate the output of the R quantile command 
> to help any parsing of the output:
> 
> SampleOutput.txt
> =====================
> R version 2.4.0 (2006-10-03)
> Copyright (C) 2006 The R Foundation for Statistical Computing
> ISBN 3-900051-07-0
> 
> R is free software and comes with ABSOLUTELY NO WARRANTY.
> You are welcome to redistribute it under certain conditions.
> Type 'license()' or 'licence()' for distribution details.
> 
>   Natural language support but running in an English locale
> 
> R is a collaborative project with many contributors.
> Type 'contributors()' for more information and
> 'citation()' on how to cite R or R packages in publications.
> 
> Type 'demo()' for some demos, 'help()' for on-line help, or
> 'help.start()' for an HTML browser interface to help.
> Type 'q()' to quit R.
> 
>> sink('quantile.txt')
>> quantile(0:100)
>> sink()
> 
> =====================
> 
> 
> quantile.txt
> =====================
>   0%  25%  50%  75% 100%
>    0   25   50   75  100
> =====================
> 
> 
> Tinn-R is written in Delphi, so its source code should be a great example of 
> a Delphi/R interface.  I've never studied the source code -- that's been on 
> my "to do" list for months --, but I'm guessing it uses RCOm, like 
> Hans-Peter suggested.  Nevertheless, Tom's example above may also be quite 
> useful.

That is a good suggestion.  I'll have to have a look at that.  Thank you!

Tom
> 
> efg
> 
> Earl F. Glynn
> Scientific Programmer
> Stowers Institute for Medical Research
> 
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| Tom Backer Johnsen, Psychometrics Unit,  Faculty of Psychology |
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