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.Dd September 12, 2019
.Dt MAT_VARWRITEAPPEND 3
.Os
.Sh NAME
.Nm Mat_VarWriteAppend
.Nd Writes/appends a MATLAB variable to an HDF5 format MATLAB MAT file.
.Sh SYNOPSIS
.Fd #include <matio.h>
.Ft int
.Fo Mat_VarWriteAppend
.Fa "mat_t *matfp"
.Fa "matvar_t *matvar"
.Fa "enum matio_compression compress"
.Fa "int dim"
.Fc
.Sh DESCRIPTION
The
.Fn Mat_VarWriteAppend
function writes (and optionally appends) the MATLAB variable
.Fa matvar
to the MAT file
.Fa matfp
which must be opened for writing.
If the MATLAB variable already exists in the MAT file, the new data is appended
to this variable along the (index 1 based) dimension
.Fa d .
The
.Fa compress
option allows the variable to be written using zlib compression if available.
If compression is not available, the variable is written uncompressed.
.Sh RETURN VALUES
The function returns 0 if the variable was successfully written/appended to the
MAT file.
Otherwise, an error value is returned.
.Sh EXAMPLES
This example program creates a MAT file named by the first argument to the
program, and writes the variable named
.Em m_pi
to the file in order to build a 2x1 array.
.Bd -literal
#include <math.h>
#include "matio.h"

int
main(int argc, char **argv)
{
    mat_t    *matfp;
    matvar_t *matvar;
    size_t    dims[2] = {1, 1};
    double    m_pi = M_PI;

    matfp = Mat_CreateVer(argv[1], NULL, MAT_FT_MAT73);
    if ( NULL == matfp ) {
        fprintf(stderr, "Error creating MAT file %s\n", argv[1]);
        return EXIT_FAILURE;
    }

    matvar = Mat_VarCreate("m_pi", MAT_C_DOUBLE, MAT_T_DOUBLE,
                           2, dims, &m_pi, 0);
    if ( NULL != matvar ) {
        int dim = 1;
        Mat_VarWriteAppend(matfp, matvar, MAT_COMPRESSION_ZLIB, dim);
        Mat_VarWriteAppend(matfp, matvar, MAT_COMPRESSION_ZLIB, dim);
        Mat_VarFree(matvar);
    }

    Mat_Close(matfp);
    return EXIT_SUCCESS;
}

.Ed
.Sh SEE ALSO
.Xr Mat_CreateVer 3 ,
.Xr Mat_Open 3 ,
.Xr Mat_VarRead 3 ,
.Xr Mat_VarWrite 3