[R] call Fortran from R

[Giacomo Santini]

Dear R users,


I have to call fortran program from within R (R 2.8.1 on ubuntu 8.10 
machine).
Suppose I have a fortran code like this (this is only a toy model, my 
working model is far more complex, but input/output is similar)


      DOUBLE PRECISION FUNCTION model(times, alfa, beta)
      DOUBLE PRECISION alfa, beta, times
      model=beta*sin(times)+alfa*cos(times)
      END FUNCTION

which is saved as model.f.

I wrote a wapper like this (saved as wrapper.f)

       SUBROUTINE model_wrapper(times, alfa, beta, answer)
       DOUBLE PRECISION times, alfa, beta, answer
       EXTERNAL model
       answer = model(times, alfa, beta)
       END SUBROUTINE

Then I compiled all this stuff

g77 -fno-second-underscore -c -fPIC model.f
g77 -fno-second-underscore -c -fPIC wrapper.f
g77 -fno-second-underscore -shared -o model.so model.o wrapper.o


 From within R

dyn.load('model.so')
model <- function(times, alfa, beta) {
      returned_data = .Fortran('model_wrapper', times=as.double(times), 
alfa=as.double(alfa),
      beta=as.double(beta), result=double(1))
      return(returned_data) }

# example run
test_1<-model(1.0,0.2,0.3)

which gives

test_1$times
[1] 1.0
$alfa
[1] 0.2
$beta
[1] 0.3
$result
[1] 147456887

where $result is clearly wrong.

I suppose I made some mistake with the handling of  data types, but I am 
not able to figure out  where.

Can someboby help me?


Giacomo

-- 
-------------------------------------------------------
Giacomo Santini PhD
Dipartimento di Biologia Evoluzionistica "Leo Pardi"
Universita' degli Studi di Firenze
Via Romana 17
I-50125 Firenze
Italy

Tel: +39 055 2288288 (DBE) - +39 0574 447727 (CESPRO)
Fax: +39 055 2288289
www.dbe.unifi.it/santini