MAT_VARCREATE(3)

💖 MAT_VARCREATE(3) 💖

okay bestie, sit down, hydrate, and let me tell you about Mat_VarCreate from the Library Functions Manual 💅 this is the girlie that makes your MAT variables. like, she builds the whole thing from scratch so you can yeet it into a MAT file later. main character energy fr fr 👑

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✨ NAME ✨

Mat_VarCreate — Creates a MAT variable structure. 🦋

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🌸 SYNOPSIS 🌸

#include <matio.h>

matvar_t *
Mat_VarCreate(const char *name, enum matio_classes class_type,
    enum matio_types data_type, int rank, const size_t *dims,
    const void *data, int opt);

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💜 DESCRIPTION 💜

So Mat_VarCreate() makes a MAT structure variable called name that is fully ready to be written to a MAT file. ✨

The class_type argument says what class the variable is, and data_type says what type the data is. Like, a double-precision class would use MAT_C_DOUBLE for the class type and MAT_T_DOUBLE for the data type. 🎀

not me about to spill the tea: in some instances the data type may not match the class type. for example, an array of integers can be written in the double-precision class by using MAT_T_INT32 for data_type. so yeah, they're allowed to be a little mismatched, it's giving versatile 💅

The rank argument is how many dimensions the data has, and the number of elements in each dimension lives in the array dims. 📐

The data argument is a pointer to the variable data, and bestie, what it points to depends on the vibe:

• For real variables, the pointer is typically a pointer to a numeric array (e.g. double, float, int, etc.).
• For complex variables, the pointer is a pointer to a mat_complex_split_t, which has pointers to the real and imaginary data as fields of the structure. 🪄
• For sparse variables, the pointer should be a mat_sparse_t *.

and there's opt at the end — that's your options slot, queen. 🫶

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🎀 RETURN VALUES 🎀

If the variable was successfully created, you get a pointer to the variable back. slay. 💖

Otherwise NULL is returned. 😭 and when you're done with the variable, it should be free'd using Mat_VarFree(). don't leave her hanging, that's rude.

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🌈 EXAMPLES 🌈

okay so here's the moment you've been waiting for. the example program below creates a MAT file named test.mat, and writes two real numeric variables x and y and a complex variable z to the file. iconic behavior honestly ✨

#include <stdlib.h>
#include <stdio.h>
#include "matio.h"

int
main(int argc,char **argv)
{
    mat_t    *matfp;
    matvar_t *matvar;
    size_t    dims[2] = {10,1};
    double    x[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9,10},
              y[10] = {11,12,13,14,15,16,17,18,19,20};
    struct mat_complex_split_t z = {x, y};

    matfp = Mat_CreateVer("test.mat", NULL, MAT_FT_DEFAULT);
    if ( NULL == matfp ) {
        fprintf(stderr, "Error creating MAT file
        return EXIT_FAILURE;
    }

    matvar = Mat_VarCreate("x", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, x, 0);
    if ( NULL == matvar ) {
        fprintf(stderr, "Error creating variable for 'x'0);
    } else {
        Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_NONE);
        Mat_VarFree(matvar);
    }

    matvar = Mat_VarCreate("y", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, y, 0);
    if ( NULL == matvar ) {
        fprintf(stderr, "Error creating variable for 'y'0);
    } else {
        Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_NONE);
        Mat_VarFree(matvar);
    }

    matvar = Mat_VarCreate("z", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, &z,
                 MAT_F_COMPLEX);
    if ( NULL == matvar ) {
        fprintf(stderr, "Error creating variable for 'z'0);
    } else {
        Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_NONE);
        Mat_VarFree(matvar);
    }

    Mat_Close(matfp);
    return EXIT_SUCCESS;
}

(and yes bestie, we copied that example character for character, no notes, no edits, periodt 💅)

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🦋 SEE ALSO 🦋

• Mat_VarCreateStruct(3)
• Mat_VarFree(3)
• Mat_VarWrite(3)

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and that's the whole page, babe. this one's from Debian, dated October 26, 2025 🎀 go forth and create your variables, you absolute legend 💖✨🫶