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📄 reading a mat-file in c.htm

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    <TD bgColor=#d9e1e1 vAlign=baseline><B>External Interfaces/API</B></TD>
    <TD align=right bgColor=#d9e1e1 vAlign=baseline><A 
      href="http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_external/ch05mat8.shtml"><IMG 
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name=reading_a_mat-file_in_c></A><!-- H2 --><A name=32276></A>
<P><FONT class=Head3 size=+1><B>Reading a MAT-File in C</B></FONT><BR>
<P><A name=32278></A>This sample program illustrates how to use the library 
routines to read and diagnose a MAT-file.</P>
<UL class=continued>
  <LI class=continued><PRE><A name=32280></A>/*
<A name=32281></A> * MAT-file diagnose program
<A name=32282></A> *
<A name=32283></A> * Calling syntax:
<A name=32284></A> *
<A name=32285></A> *   matdgns &lt;matfile.mat&gt;
<A name=32286></A> *
<A name=32287></A> * It diagnoses the MAT-file named &lt;matfile.mat&gt;.
<A name=32288></A> *
<A name=32289></A> * This program demonstrates the use of the following functions:
<A name=32290></A> *
<A name=32291></A> *  matClose
<A name=32292></A> *  matGetDir
<A name=32293></A> *  matGetNextVariable
<A name=32294></A> *  matGetNextVariableInfo
<A name=32295></A> *  matOpen
<A name=32296></A> *  
<A name=32297></A> *  Copyright (c) 1984-2000 The MathWorks, Inc.
<A name=40201></A> *  $Revision: 1.9 $
<A name=32298></A> */
<A name=32299></A>
<A name=40213></A>#include &lt;stdio.h&gt;
<A name=40214></A>#include &lt;stdlib.h&gt;
<A name=40215></A>#include "mat.h"
<A name=40216></A>
<A name=40217></A>int diagnose(const char *file) {
<A name=40218></A>  MATFile *pmat;
<A name=40219></A>  char **dir;
<A name=40220></A>  const char *name;
<A name=40221></A>  int ndir;
<A name=40222></A>  int i;
<A name=40223></A>  mxArray *pa;
<A name=40224></A>  
<A name=40225></A>  printf("Reading file %s...\n\n", file);
<A name=40226></A>
<A name=40227></A>  /* Open file to get directory. */
<A name=40230></A>  pmat = matOpen(file, "r");
<A name=40231></A>  if (pmat == NULL) {
<A name=40232></A>    printf("Error opening file %s\n", file);
<A name=40233></A>    return(1);
<A name=40234></A>  }
<A name=40235></A>  
<A name=40236></A>  /* Get directory of MAT-file. */
<A name=40239></A>  dir = matGetDir(pmat, &amp;ndir);
<A name=40240></A>  if (dir == NULL) {
<A name=40241></A>    printf("Error reading directory of file %s\n", file);
<A name=40242></A>    return(1);
<A name=40243></A>  } else {
<A name=40244></A>    printf("Directory of %s:\n", file);
<A name=40245></A>    for (i=0; i &lt; ndir; i++)
<A name=40246></A>      printf("%s\n", dir[i]);
<A name=40247></A>  }
<A name=40248></A>  mxFree(dir);
<A name=40249></A>
<A name=40250></A>  /* In order to use matGetNextXXX correctly, reopen file to 
     read in headers. */
<A name=40251></A>  if (matClose(pmat) != 0) {
<A name=40252></A>    printf("Error closing file %s\n",file);
<A name=40253></A>    return(1);
<A name=40254></A>  }
<A name=40255></A>  pmat = matOpen(file, "r");
<A name=40256></A>  if (pmat == NULL) {
<A name=40257></A>    printf("Error reopening file %s\n", file);
<A name=40258></A>    return(1);
<A name=40259></A>  }
<A name=40260></A>
<A name=40261></A>  /* Get headers of all variables. */
<A name=40262></A>  printf("\nExamining the header for each variable:\n");
<A name=40263></A>  for (i=0; i &lt; ndir; i++) {
<A name=40264></A>    pa = matGetNextVariableInfo(pmat, &amp;name);
<A name=40265></A>    if (pa == NULL) {
<A name=40266></A>      printf("Error reading in file %s\n", file);
<A name=40267></A>      return(1);
<A name=40268></A>    }
<A name=40269></A>    /* Diagnose header pa. */
<A name=40270></A>    printf("According to its header, array %s has %d 
dimensions\n",
<A name=40271></A>           name, mxGetNumberOfDimensions(pa));
<A name=40272></A>    if (mxIsFromGlobalWS(pa))
<A name=40273></A>      printf("  and was a global variable when saved\n");
<A name=40274></A>    else
<A name=40275></A>      printf("  and was a local variable when saved\n");
<A name=40276></A>    mxDestroyArray(pa);
<A name=40277></A>  }
<A name=40278></A>
<A name=40279></A>  /* Reopen file to read in actual arrays. */
<A name=40280></A>  if (matClose(pmat) != 0) {
<A name=40281></A>    printf("Error closing file %s\n",file);
<A name=40282></A>    return(1);
<A name=40283></A>  }
<A name=40284></A>  pmat = matOpen(file, "r");
<A name=40285></A>  if (pmat == NULL) {
<A name=40286></A>    printf("Error reopening file %s\n", file);
<A name=40287></A>    return(1);
<A name=40288></A>  }
<A name=40289></A>
<A name=40290></A>  /* Read in each array. */
<A name=40291></A>  printf("\nReading in the actual array contents:\n");
<A name=40292></A>  for (i=0; i&lt;ndir; i++) {
<A name=40293></A>    pa = matGetNextVariable(pmat, &amp;name);
<A name=40294></A>    if (pa == NULL) {
<A name=40295></A>      printf("Error reading in file %s\n", file);
<A name=40296></A>      return(1);
<A name=40297></A>    } 
<A name=40298></A>    /*
<A name=40299></A>     * Diagnose array pa
<A name=40300></A>     */
<A name=40301></A>    printf("According to its contents, array %s has %d
            dimensions\n", name, mxGetNumberOfDimensions(pa));
<A name=40303></A>    if (mxIsFromGlobalWS(pa))
<A name=40304></A>      printf("  and was a global variable when saved\n");
<A name=40305></A>    else
<A name=40306></A>      printf("  and was a local variable when saved\n");
<A name=40307></A>    mxDestroyArray(pa);
<A name=40308></A>  }
<A name=40309></A>
<A name=40310></A>  if (matClose(pmat) != 0) {
<A name=40311></A>    printf("Error closing file %s\n",file);
<A name=40312></A>    return(1);
<A name=40313></A>  }
<A name=40314></A>  printf("Done\n");
<A name=40315></A>  return(0);
<A name=40316></A>}
<A name=40317></A>
<A name=40318></A>
<A name=40442></A>int main(int argc, char **argv)
<A name=40319></A>{
<A name=40321></A>  int result;
<A name=40322></A>
<A name=40323></A>  if (argc &gt; 1)
<A name=40324></A>    result = diagnose(argv[1]);
<A name=40325></A>  else{
<A name=40326></A>    result = 0;
<A name=40327></A>    printf("Usage: matdgns &lt;matfile&gt;");
<A name=40328></A>    printf(" where &lt;matfile&gt; is the name of the MAT-file");
<A name=40329></A>    printf(" to be diagnosed\n");
<A name=40330></A>  }
<A name=40332></A>  return (result==0) ? EXIT_SUCCESS : EXIT_FAILURE;
<A name=40334></A>}
</PRE></LI></UL>
<P><A name=33243></A>After compiling and linking this program, you can view its 
results.</P>
<UL class=continued>
  <LI class=continued><PRE><A name=32421></A>matdgns mattest.mat
<A name=32422></A>Reading file mattest.mat...
<A name=32423></A> 
<A name=32424></A>Directory of mattest.mat:
<A name=32425></A>GlobalDouble
<A name=32426></A>LocalString
<A name=32427></A>LocalDouble
<A name=32428></A> 
<A name=32429></A>Examining the header for each variable:
<A name=32430></A>According to its header, array GlobalDouble has 2 dimensions
<A name=32431></A>  and was a global variable when saved
<A name=32432></A>According to its header, array LocalString has 2 dimensions
<A name=32433></A>  and was a local variable when saved
<A name=32434></A>According to its header, array LocalDouble has 2 dimensions
<A name=32435></A>  and was a local variable when saved
<A name=32436></A> 
<A name=32437></A>Reading in the actual array contents:
<A name=32438></A>According to its contents, array GlobalDouble has 2 dimensions
<A name=32439></A>  and was a global variable when saved
<A name=32440></A>According to its contents, array LocalString has 2 dimensions
<A name=32441></A>  and was a local variable when saved
<A name=32442></A>According to its contents, array LocalDouble has 2 dimensions
<A name=32443></A>  and was a local variable when saved
<A name=32444></A>Done
</PRE></LI></UL>
<P><BR>
<P>
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    <TD align=left>&nbsp;Examples of MAT-Files</TD>
    <TD>&nbsp;</TD>
    <TD align=right>Creating a MAT-File in Fortran&nbsp;</TD>
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