Initializing a 2D array dynamically allocated

I'm working with 2D arrays so that I can perform many calculations with them, just as matrices with numbers on them. Right now I change the dimensions of the matrices within the code, so I know what the dimensions are.
I created a dynamically allocated 2d array, but I can't figure out how to initialize it. For instance:

Code:

---

int ROW=2;
int COL=2;

int main()
{
        float **mat1=(float **)malloc(ROW*COL*sizeof(float *));

        mat1[ROW][COL]= { {5.3, 7.4},{1.1, 3.7} };

.
.
.

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Trying to initialize the array this way, I get an error from the compiler, which says: "expected expression before "{" token ". I need to find a way to initialize the whole array with a single instruction, any help would greatly be appreciated.

Thanks in advance!

malloc() storage for all the elements before proceeding to initialize it.

If you get rid of the malloc on the first line, then specify float mat1... on the second line it should work.

If you insist upon using malloc, you will need to initialize it in loops.

Did you include stdlib.h?

There is no need (and some risk) to casting the return from malloc().

You have (apparently), allocated a pointer to a 2D array, but you have not yet allocated the pointers for each row of the array:

Code:

---

for(i = 0; i < NumberOfRowsYouWant; i++)
  array[i] = malloc(columnsYouHave * sizeof(float));  //not float * for this one

---

When you are done, free the row pointers first, and then the array pointer, (IOW, free them in reverse of the order you created them in).

An example:

Code:

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/* dynamically creates a 2D array of pointers, in C */

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

//void allocate2D(double **dat2, int nrows, int ncols);
double** allocate2D(int nrows, int ncols);

int main() {
  int i,j, rows, cols;
  double **dat;

  printf("\n\n\n How many rows do you want?\n ");
  scanf("%d", &rows);
  (void) getchar();
  printf(" How many columns do you want?\n ");
  scanf("%d", &cols);
  (void) getchar();

  dat = allocate2D(rows, cols);
  for(i=0;i<rows;i++) {
    for(j=0;j<cols;j++) {
      dat[i][j] = i+j;
    }
  }
  for(i=0;i<rows;i++) {
      for(j=0;j<cols;j++)
        printf("\n%.3lf", dat[i][j]);
  }
 
  for(i=0;i<rows;i++)
    free(dat[i]);
  free(dat);

  printf("\n\t\t\t    press enter when ready");
  (void) getchar();
  return 0;
}
double** allocate2D(int nrows, int ncols) {
  int i;
  double **dat2;
  /*  allocate array of pointers  */
  dat2 = malloc( nrows*sizeof(double*));
   
  if(dat2==NULL) {
    printf("\nError allocating memory\n");
    exit(1);
  }
  /*  allocate each row  */
  for(i = 0; i < nrows; i++) {
    dat2[i] = malloc( ncols*sizeof(double));
  }
  if(dat2[i-1]==NULL) {
    printf("\nError allocating memory\n");
    exit(1);
  }
  return dat2;
}

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Thanks for your quick answers.
I removed the cast, and allocated pointers for each row of the array. Then I freed the pointers.
But in the statement for statement:mat1[ROW][COL]= { {5.3, 7.4},{1.1, 3.7} }; , there is still the same error: "expected expression before "{" token "

Is it really possible to initialize this way? or it is necessary a loop as some people mentioned.
Thanks

No, it's not possible. You can only use that style of initializer when you declare the variable:

Code:

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int foo[ 2 ][ 2 ] = { { 1, 2 }, { 3, 4 } };

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That's OK. This is not:

Code:

---

int foo[ 2 ][ 2 ];
foo = { { 1, 2 }, { 3, 4 } };

---

Quzah.