External Interfaces/API |

**Passing Arrays of Strings**

Passing arrays of strings adds a slight complication to the example in the previous section, Passing Strings. Because MATLAB stores elements of a matrix by column instead of by row, it is essential that the size of the string array be correctly defined in the Fortran MEX-file. The key point is that the row and column sizes as defined in MATLAB must be reversed in the Fortran MEX-file. Consequently, when returning to MATLAB, the output matrix must be transposed.

This example places a string array/character matrix into MATLAB as output arguments rather than placing it directly into the workspace. Inside MATLAB, call this function by typing

You will get the matrix `mystring`

of size 5-by-15. There are some manipulations that need to be done here. The original string matrix is of the size 5-by-15. Because of the way MATLAB reads and orients elements in matrices, the size of the matrix must be defined as `M=15`

and `N=5`

from the MEX-file. After the matrix is put into MATLAB, the matrix must be transposed.

C============================================================== = C passstr.f C Example for illustrating how to pass a character matrix C from Fortran to MATLAB. C C Passes a string array/character matrix into MATLAB as C output arguments rather than placing it directly into the C workspace. C C This is a MEX-file for MATLAB. C Copyright (c) 1984-2000 The MathWorks, Inc. C $Revision: 1.9 $ C============================================================== = C The gateway routine subroutine mexFunction(nlhs, plhs, nrhs, prhs) C-------------------------------------------------------------- C (pointer) Replace integer by integer*8 on the DEC Alpha C platform. integer plhs(*), prhs(*) integer p_str, mxCreateString C-------------------------------------------------------------- integer nlhs, nrhs integer i character*75 thestring character*15 string(5) C Create the string to passed into MATLAB. string(1) = 'MATLAB ' string(2) = 'The Scientific ' string(3) = 'Computing ' string(4) = 'Environment ' string(5) = ' by TMW, Inc.' C Concatenate the set of 5 strings into a long string. thestring = string(1) do 10 i=2,6 thestring = thestring(:((i-1)*15)) // string(i) 10 continue C Create the string matrix to be passed into MATLAB. C Set the matrix size to be M=15 and N=5. p_str = mxcreatestring(thestring) call mxSetM(p_str, 15) call mxSetN(p_str, 5) C Transpose the resulting matrix in MATLAB. call mexCallMATLAB(1, plhs, 1, p_str, 'transpose') return end

at the MATLAB prompt produces this result

Passing Strings | Passing Matrices |