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MAT_VARCREATESTRUCT(3) Library Functions Manual MAT_VARCREATESTRUCT(3)

NAME

Mat_VarCreateStruct — Creates a structure variable.

SYNOPSIS

#include <matio.h>

matvar_t *
Mat_VarCreateStruct(const char *name, int rank, const size_t *dims, const char *const *fields, unsigned nfields);

DESCRIPTION

The () function creates a structure variable named name that can be written to a MAT file.

RETURN VALUES

If the structure variable was successfully created, a pointer to the variable is returned. Otherwise NULL is returned. The structure variable pointer should be free'd when no longer needed using Mat_VarFree(). The names of the fields are copied in the function, and thus should be released after calling the function if necessary.

DEPRECATED

This function is deprecated since version 1.5.30. Use Mat_VarCreateStruct2 instead.

EXAMPLES

This example program opens a MAT file named by the first argument to the program, and writes a structure named to the file.

#include "matio.h"

int
main(int argc, char **argv)
{
    mat_t    *matfp;
    matvar_t *matvar;
    matvar_t *field;
    const char *fields[2] = {"field1", "field2"};
    double       data1 = 1, data2 = 2;
    size_t       dims[2] = {1, 1};

    matfp = Mat_Open(argv[1], MAT_ACC_RDWR);
    if ( NULL == matfp ) {
        fprintf(stderr, "Error opening MAT file %s0, argv[1]);
        return EXIT_FAILURE;
    }

    dims[0] = 1; dims[1] = 1;
    matvar = Mat_VarCreateStruct("a", 2, dims, fields, 2);
    if ( NULL == matvar ) {
        Mat_Close(matfp);
        return EXIT_FAILURE;
    }

    field = Mat_VarCreate(NULL, MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, &data1,
                MAT_F_DONT_COPY_DATA);
    Mat_VarSetStructFieldByName(matvar, "field1", 0, field);

    field = Mat_VarCreate(NULL, MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, &data2,
                MAT_F_DONT_COPY_DATA);
    Mat_VarSetStructFieldByName(matvar, "field2", 0, field);

    Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_NONE);
    Mat_VarFree(matvar);

    Mat_Close(matfp);
    return EXIT_SUCCESS;
}

SEE ALSO

Mat_VarCreateStruct2(3), Mat_VarCreate(3), Mat_VarSetStructFieldByName(3)

January 5, 2026 Nixpkgs