mex return two values.

hi.

i am trying to mex(in fortran-matlab).

i want to two values in matlab using mex, i make fortran and put in to 4 mwpointer x-input, y-output, a-input, b-input.

and make fortran files, but it can't read two values.

========================================================================================================

      real*8  x, y, A, B, z

C-----------------------------------------------------------------------

      if(nrhs .ne. 2) then
         call mexErrMsgIdAndTxt ('MATLAB:timestwo:nInput',
     +                           'One input required.')
      elseif(nlhs .gt. 2) then
         call mexErrMsgIdAndTxt ('MATLAB:timestwo:nOutput',
     +                           'Too many output arguments.')
      endif

      if(mxIsNumeric(prhs(2)) .eq. 0) then
         call mexErrMsgIdAndTxt ('MATLAB:timestwo:NonNumeric',
     +                           'Input must be a number.')
      endif

      mrows = mxGetM(prhs(1))
      ncols = mxGetN(prhs(2))
      size = mrows*ncols

      x_ptr = mxGetPr(prhs(1))
      A_ptr = mxGetPr(prhs(2))
      call mxCopyPtrToReal8(x_ptr,x,size)
      call mxCopyPtrToReal8(A_ptr,A,size)

      plhs(1) = mxCreateDoubleMatrix(mrows,ncols,0)
      y_ptr = mxGetPr(plhs(1))
      B_ptr = mxGetPr(plhs(2))

      call timestwo(y, x, B, A, z)

      call mxCopyReal8ToPtr(y,y_ptr,size)
      call mxCopyReal8ToPtr(B,B_ptr,size)     

      return
      end

C----------------------------------------------------------------------- C Computational routine

      subroutine timestwo(y, x, B, A, z)

      real*8 y, x, B, A, z

      y = 2.0 * x
      B = 2.0 * A

      i = y, j = b

      z=(i,j)

      return
      end

======================================================================================================

i'm so hard to understand about prhs,plhs..

is this program correct?

help me please.

[Chaitra]

Have you referred to this link?

http://www.mathworks.com/help/matlab/matlab_external/create-fortran-source-mex-file.html

It gives a description as to how to Create Fortran Source MEX-File.

[James Tursa]

Rather than comment on the multiple problems with the above routine, may I start with asking you what you want it to do? Are you simply trying to input two double scalars, multiply both of them by 2, and then return both of the results back to the MATLAB workspace?

[Tejas M U]

If you want to understand about prhs, plhs, you may want to refer to the following: http://www.mathworks.com/help/matlab/matlab_external/data-flow-in-fortran-mex-files.html

Answer 1

[Jan]

You have created the 1st output by:

plhs(1) = mxCreateDoubleMatrix(mrows,ncols,0)

An equivalent method is required for the 2nd output also, only with plhs(2).