Transpose matrix (w pointers)

[agabriel]

Hello,

Okay I'm stumped and can't figure out why this code chunk isn't working properly (works on square matrixs; everything else doesn't work)....

uint8 * imageTranspose( uint8 *im ){
    uint8   *im_transpose;
    int     x, y, org_offset, tran_offset;
    int     im_size  = dims[0] * dims[1];

    if ( (im_transpose = malloc(sizeof(uint16) * im_size)) == NULL )
        mexErrMsgTxt("trans im malloc failed...n");

    //Transpose
    for(x=0;x<dims[0]; x++){
        for(y=0;y<dims[1]; y++){
            org_offset = x+(y*dims[0]); //So X=X & Y=Y
            tran_offset= y-(x*dims[1]); //So X=Y & Y=X
            *(im_transpose+tran_offset) = *(im+org_offset); 
            //mexPrintf("%dt%dn",*(im+org_offset),*(im_transpose+tran_offset));
        }
    }

    return im_transpose;
}

At the end of the day I will not be using Matlab and therefore I'm just using it as a prototyping tool. Does anyone have any ideas by chance?

Thanks,
Anthony

[Dave Sinkula]

I might do a transpose like this.

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

int **create    (                                size_t rows, size_t cols );
void  destroy   (       int             **array, size_t rows);
int **transpose ( const int *const *const array, size_t rows, size_t cols);
void  print     ( const int *const *const array, size_t rows, size_t cols );

int main(void)
{
   size_t rows = 3, cols = 5;
   int **array = create(rows, cols);
   int **trans = transpose(array, rows, cols);
   print(array, rows, cols);
   print(trans, cols, rows);
   destroy(array, rows);
   destroy(trans, cols);
   return 0;
}

int **create(size_t rows, size_t cols)
{
   size_t r, c;
   int k = 0;
   int **array = malloc(rows * sizeof *array);
   if ( array )
   {
      for ( r = 0; r < rows; ++r )
      {
         array[r] = malloc(cols * sizeof *array[r]);
         if ( !array[r] )
         {
            destroy(array, r - 1);
            return NULL;
         }
         for ( c = 0; c < cols; ++c )
         {
            array[r][c] = k++;
         }
      }
   }
   return array;
}

int **transpose(const int *const *const array, size_t rows, size_t cols)
{
   size_t r, c;
   int **result = malloc(cols * sizeof *result);
   if ( result )
   {
      for ( r = 0; r < cols; ++r )
      {
         result[r] = malloc(rows * sizeof *result[r]);
         if ( !result[r] )
         {
            destroy(result, r - 1);
            return NULL;
         }
         for ( c = 0; c < rows; ++c )
         {
            [B]result[r][c] = array[c][r];[/B]
         }
      }
   }
   return result;
}

void destroy(int **array, size_t rows)
{
   size_t r;
   for ( r = 0; r < rows; ++r )
   {
      free(array[r]);
   }
   free(array);
}

void print(const int *const *const array, size_t rows, size_t cols)
{
   size_t r, c;
   for ( r = 0; r < rows; ++r )
   {
      for ( c = 0; c < cols; ++c )
      {
         printf("%2d ", array[r][c]);
      }
      putchar('\n');
   }
   putchar('\n');
}

/* my output
 0  1  2  3  4
 5  6  7  8  9
10 11 12 13 14

 0  5 10
 1  6 11
 2  7 12
 3  8 13
 4  9 14
*/

[agabriel]

I like that - that looks good.

Thanks,
Anthony

[sumantra529]

100% correct matrix Transpose program with out any pointer without any complicity.
-------------------------------------------------------------------

#include<stdio.h>
#include<conio.h>
void main()
{
	int a[10][10],i,j,n,m,save;
	clrscr();
	printf("Enter The Rows And Cloumns And Of The First Matrix:");
	scanf("%d%d",&m,&n);
	printf("\nEnter Elements Of The First Matrix:\n");
	for(i=0;i<m;i++)
	{
		for(j=0;j< n;j++)
		{
			scanf("%d",&a[i][j]);
		}
	}
	
	printf("The First Matrix Is:\n");
	for(i=0;i<m;i++)
	{
		for(j=0;j<n;j++)
		{
			printf("%d",a[i][j]); //print the first matrix
		}
		printf("\n");
	}
	for (i = 0; i < 4; i++)
	{
		 for (j = 0; j < 4; j++)
		{
			save = a[i][j];
			a[i][j] = a[j][i];
			a[j][i] = save;
		}
	}
	printf("After inverse of Matrix Is:\n");
	for(i=0;i<m;i++)
	{
		for(j=0;j<n;j++)
		{
			printf("%d",a[j][i]);
		}
		printf("\n");
	}
	getch();
}

[Clockowl]

Nice job reviving a 2 year old thread? ;)