Lua C API: Initializing a variable matrix in a structure C

I'm trying to create an userdata with Lua C API with a metatable associated where I will collect a matrix.

What I can't get is how to set every component of the initialized matrix to zero.

I compile my Lua module C code as I described here.

The C code I have is the following:

#include "lauxlib.h"
#include "lua.h"

typedef struct {
    LUA_NUMBER data[1][1];
    int row;
    int col;
}matrix;


// Create a matrix full of zeros
static int lb_newmatrix(lua_State *L)
{

    // Variable declarations
    int i,j;
    matrix *temp;

    // Input checks
    if (lua_gettop(L)!=2)
    {
       lua_pushstring(L,"\n Two input required");
       lua_error(L);
    }

    //--> Check I° index m riga
    luaL_checktype(L,1,LUA_TNUMBER);
    if (lua_tonumber(L,1)<0)
    {
        lua_pushstring(L,"\nRow number must be positive");
        lua_error(L);
    }

    //--> Check II° index n colonna
    luaL_checktype(L,2,LUA_TNUMBER);
    if (lua_tonumber(L,2)<0)
    {
        lua_pushstring(L,"\nColumn number must be positive");
        lua_error(L);
    }

    // Computation of memory allocation
    int m = lua_tonumber(L,1);
    int n = lua_tonumber(L,2);
    size_t nbyte = 2*sizeof(int)+sizeof(LUA_NUMBER)*m*n;
    size_t nbyte2 = sizeof(matrix)+sizeof(LUA_NUMBER)*(m*n-1);

    // Memory allocation
    temp = (matrix *)lua_newuserdata(L,nbyte);

    // Matrix dimension setting
    temp->row = m;
    temp->col = n;

    // Matrix inizialization
    /* PROBLEM HERE */
    for (i=1;i==m;i++)
    {
        for(j=1;j==n;j++)
        {
            temp->data[i][j] = 0;
        }
    }

    //-------------------------------
    // If I de-comment these line,
    // the matrix is written but 
    // element with equal sum indices
    // rewrite!!!
    //-------------------------------
    // temp->data[1][1] = nbyte;
    // temp->data[1][2] = nbyte2;
    // temp->data[1][3] = 13;
    // temp->data[2][1] = nbyte2;
    // temp->data[2][2] = 22;
    // temp->data[2][3] = 23; 
    // temp->data[3][1] = 31;
    // temp->data[3][2] = 32;
    // temp->data[3][3] = 33;

    // Link the userdata to the metatable "basic"
    luaL_getmetatable(L,"basic");
    lua_setmetatable(L,-2);

    return 1;
}

static int lb_index(lua_State *L)
{
    /* Check input Numbers */
    if (lua_gettop(L)>3)
    {
       lua_pushstring(L,"\nOnly two inputs are needed:\n1) Point\n2) N° row\n3) N° col");
       lua_error(L);
    }

    /* Check if the first input is userdata basic */
    matrix *temp = (matrix *)luaL_checkudata(L,1,"basic");

    /* I° index check ROW */
    luaL_checktype(L,2,LUA_TNUMBER); 
    if (lua_tointeger(L,2)<0||lua_tointeger(L,2)>temp->row)
    {
        lua_pushstring(L,"\n First index should be 1 to n");
        lua_error(L);
    }

    /* II° index check COLUMN */
    luaL_checktype(L,3,LUA_TNUMBER);
    if (lua_tointeger(L,3)<0||lua_tointeger(L,3)>temp->col)
    {
        lua_pushstring(L,"\n Second index should be 1 to m");
        lua_error(L);
    }

    int row = lua_tointeger(L,2);
    int col = lua_tointeger(L,3);

    /* Insert the index value of userdata on top of the stack */
    lua_pushnumber(L,temp->data[row][col]);

    return 1;
}


/**********************
 * MODULE DECLARATION *
 **********************/
static const struct luaL_Reg LuaBasic_f [] = {//
        {"NewMatrix",lb_newmatrix},
        {   "__index",  lb_index},
        {       NULL,        NULL}};

static const struct luaL_Reg LuaBasic_m [] = {//
        {        NULL,      NULL}};

LUA_API int luaopen_LuaBasic(lua_State *L)
{
    /* Insert basic metatable  "basic" into the stack */
    luaL_newmetatable(L,"basic");

    /* Copy the "basic" metatable
       and push it into the stack */
    lua_pushvalue(L,-1);

    /* basic["__index"] = basic */
    lua_setfield(L,-2,"__index");

    /* register all the function
       into LuaBasic_m into the
       basic table metatable */
    luaL_setfuncs(L,LuaBasic_m,0);

    luaL_newlib(L,LuaBasic_f);
    return 1;
}

The related Lua Code is the following:

lb = require("LuaBasic")
A = lb.NewMatrix(3,3)
print(A)
print("--------------")
print(lb.__index(A,1,1))
print(lb.__index(A,1,2))
print(lb.__index(A,1,3))
print(lb.__index(A,2,1))
print(lb.__index(A,2,2))
print(lb.__index(A,2,3))
print(lb.__index(A,3,1))
print(lb.__index(A,3,2))
print(lb.__index(A,3,3))
print("--------------")
print("row = "..lb.GetRow(A))
print("col = "..lb.GetCol(A))

and the output I get is:

userdata: 007C2940
--------------
1.#QNAN
1.#QNAN
1.#QNAN
1.#QNAN
1.#QNAN
1.#QNAN
1.#QNAN
1.#QNAN
1.#QNAN
--------------
row = 3
col = 3

I don't understand why I can't write the zero values into initialized matrix.

What do I do wrong?