External Interfaces/API

Calling MATLAB From a Fortran Application

This program, fengdemo.f, illustrates how to call the engine functions from a stand-alone Fortran program.

• C==============================================================
  =
  C     fengdemo.f
  C
  C     This program illustrates how to call the MATLAB
  C     Engine functions from a Fortran program.
  C
  C Copyright (c) 1984-2000 by The MathWorks, Inc.
  C $Revision: 1.9 $
  C==============================================================
  =
  
        program main
  C--------------------------------------------------------------
  -
  C     (pointer) Replace integer by integer*8 on the DEC Alpha
  C     64-bit platform
  
        integer engOpen, engGetVariable, mxCreateDoubleMatrix
        integer mxGetPr
        integer ep, T, D 
  C--------------------------------------------------------------
  -
  
  C     Other variable declarations here
        double precision time(10), dist(10)
        integer engPutVariable, engEvalString, engClose
        integer temp, status
        data time / 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0,
                     9.0, 10.0 /
  
        ep = engOpen('matlab ')
  
        if (ep .eq. 0) then
           write(6,*) 'Can''t start MATLAB engine'
           stop
        endif
  
        T = mxCreateDoubleMatrix(1, 10, 0)
        call mxCopyReal8ToPtr(time, mxGetPr(T), 10)
  C
  C     Place the variable T into the MATLAB workspace.
  C
        status = engPutVariable(ep, 'T', T)
  
        if (status .ne. 0) then 
           write(6,*) 'engPutVariable failed'
           stop
        endif
  C
  C     Evaluate a function of time, distance = (1/2)g.*t.^2
  C     (g is the acceleration due to gravity).
  C
        if (engEvalString(ep, 'D = .5.*(-9.8).*T.^2;') .ne. 0) then
           write(6,*) 'engEvalString failed'
           stop
        endif
  C
  C     Plot the result.
  C
        if (engEvalString(ep, 'plot(T,D);') .ne. 0) then 
           write(6,*) 'engEvalString failed'
           stop
        endif
  
        if (engEvalString(ep, 'title(''Position vs. Time'')')
        .ne. 0) then
           write(6,*) 'engEvalString failed'
           stop
        endif
  
        if (engEvalString(ep, 'xlabel(''Time (seconds)'')') 
        .ne. 0) then
           write(6,*) 'engEvalString failed'
           stop
        endif
        if (engEvalString(ep, 'ylabel(''Position (meters)'')') 
        .ne. 0) then
           write(6,*) 'engEvalString failed'
           stop
        endif
  C
  C     Read from console to make sure that we pause long enough to 
  C     be able to see the plot.
  C
        print *, 'Type 0 <return> to Exit'
        print *, 'Type 1 <return> to continue'
  
        read(*,*) temp
  
        if (temp.eq.0) then
           print *, 'EXIT!'
           stop
        end if
  
        if (engEvalString(ep, 'close;') .ne. 0) then
           write(6,*) 'engEvalString failed'
           stop
        endif 
        
        D = engGetVariable(ep, 'D')
        call mxCopyPtrToReal8(mxGetPr(D), dist, 10)
        print *, 'MATLAB computed the following distances:'
        print *, '  time(s)  distance(m)'
        do 10 i=1,10
           print 20, time(i), dist(i)
   20      format(' ', G10.3, G10.3)
   10   continue
       
        call mxDestroyArray(T)
        call mxDestroyArray(D)
        status = engClose(ep)
        
        if (status .ne. 0) then 
           write(6,*) 'engClose failed'
           stop
        endif
  
        stop
        end
  

Executing this program launches MATLAB, sends it data, and plots the results.

The program continues with

• Type 0 <return> to Exit
  Type 1 <return> to continue
  

Entering 1 at the prompt continues the program execution.

• 1
   MATLAB computed the following distances:
     time(s)  distance(m)
     1.00     -4.90    
     2.00     -19.6    
     3.00     -44.1    
     4.00     -78.4    
     5.00     -123.    
     6.00     -176.    
     7.00     -240.    
     8.00     -314.    
     9.00     -397.    
     10.0     -490.    
  

Finally, the program frees memory, closes the MATLAB engine, and exits.

Examples of Calling Engine Functions

Attaching to an Existing MATLAB Session