External Interfaces/API

Reading a MAT-File in C

This sample program illustrates how to use the library routines to read and diagnose a MAT-file.

• /*
   * MAT-file diagnose program
   *
   * Calling syntax:
   *
   *   matdgns <matfile.mat>
   *
   * It diagnoses the MAT-file named <matfile.mat>.
   *
   * This program demonstrates the use of the following functions:
   *
   *  matClose
   *  matGetDir
   *  matGetNextVariable
   *  matGetNextVariableInfo
   *  matOpen
   *  
   *  Copyright (c) 1984-2000 The MathWorks, Inc.
   *  $Revision: 1.9 $
   */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include "mat.h"
  
  int diagnose(const char *file) {
    MATFile *pmat;
    char **dir;
    const char *name;
    int ndir;
    int i;
    mxArray *pa;
    
    printf("Reading file %s...\n\n", file);
  
    /* Open file to get directory. */
    pmat = matOpen(file, "r");
    if (pmat == NULL) {
      printf("Error opening file %s\n", file);
      return(1);
    }
    
    /* Get directory of MAT-file. */
    dir = matGetDir(pmat, &ndir);
    if (dir == NULL) {
      printf("Error reading directory of file %s\n", file);
      return(1);
    } else {
      printf("Directory of %s:\n", file);
      for (i=0; i < ndir; i++)
        printf("%s\n", dir[i]);
    }
    mxFree(dir);
  
    /* In order to use matGetNextXXX correctly, reopen file to 
       read in headers. */
    if (matClose(pmat) != 0) {
      printf("Error closing file %s\n",file);
      return(1);
    }
    pmat = matOpen(file, "r");
    if (pmat == NULL) {
      printf("Error reopening file %s\n", file);
      return(1);
    }
  
    /* Get headers of all variables. */
    printf("\nExamining the header for each variable:\n");
    for (i=0; i < ndir; i++) {
      pa = matGetNextVariableInfo(pmat, &name);
      if (pa == NULL) {
        printf("Error reading in file %s\n", file);
        return(1);
      }
      /* Diagnose header pa. */
      printf("According to its header, array %s has %d 
  dimensions\n",
             name, mxGetNumberOfDimensions(pa));
      if (mxIsFromGlobalWS(pa))
        printf("  and was a global variable when saved\n");
      else
        printf("  and was a local variable when saved\n");
      mxDestroyArray(pa);
    }
  
    /* Reopen file to read in actual arrays. */
    if (matClose(pmat) != 0) {
      printf("Error closing file %s\n",file);
      return(1);
    }
    pmat = matOpen(file, "r");
    if (pmat == NULL) {
      printf("Error reopening file %s\n", file);
      return(1);
    }
  
    /* Read in each array. */
    printf("\nReading in the actual array contents:\n");
    for (i=0; i<ndir; i++) {
      pa = matGetNextVariable(pmat, &name);
      if (pa == NULL) {
        printf("Error reading in file %s\n", file);
        return(1);
      } 
      /*
       * Diagnose array pa
       */
      printf("According to its contents, array %s has %d
              dimensions\n", name, mxGetNumberOfDimensions(pa));
      if (mxIsFromGlobalWS(pa))
        printf("  and was a global variable when saved\n");
      else
        printf("  and was a local variable when saved\n");
      mxDestroyArray(pa);
    }
  
    if (matClose(pmat) != 0) {
      printf("Error closing file %s\n",file);
      return(1);
    }
    printf("Done\n");
    return(0);
  }
  
  
  int main(int argc, char **argv)
  {
    int result;
  
    if (argc > 1)
      result = diagnose(argv[1]);
    else{
      result = 0;
      printf("Usage: matdgns <matfile>");
      printf(" where <matfile> is the name of the MAT-file");
      printf(" to be diagnosed\n");
    }
    return (result==0) ? EXIT_SUCCESS : EXIT_FAILURE;
  }
  

After compiling and linking this program, you can view its results.

• matdgns mattest.mat
  Reading file mattest.mat...
   
  Directory of mattest.mat:
  GlobalDouble
  LocalString
  LocalDouble
   
  Examining the header for each variable:
  According to its header, array GlobalDouble has 2 dimensions
    and was a global variable when saved
  According to its header, array LocalString has 2 dimensions
    and was a local variable when saved
  According to its header, array LocalDouble has 2 dimensions
    and was a local variable when saved
   
  Reading in the actual array contents:
  According to its contents, array GlobalDouble has 2 dimensions
    and was a global variable when saved
  According to its contents, array LocalString has 2 dimensions
    and was a local variable when saved
  According to its contents, array LocalDouble has 2 dimensions
    and was a local variable when saved
  Done
  

Examples of MAT-Files

Creating a MAT-File in Fortran