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Transpose a matrix

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Join Date: Feb 2005

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mariners95 mariners95 is offline

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Transpose a matrix

Feb 13th, 2005

I need help with transposing a matrix.

I already did the transpose matrix using 2 arrays.

But I can't figure out how to do it using only one array.
So read a matrix and create the transpose within itself.
Do I use the swap or what?

Any help would be great.

Later

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Narue

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Re: Transpose a matrix

Feb 13th, 2005

If it's a square matrix then you can do it with something like this:

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 C Syntax (Toggle Plain Text) 
for (int i = 0; i < 4; i++) {
  for (int j = i + 1; j < 4; j++) {
    int save = matrix[i][j];
    matrix[i][j] = matrix[j][i];
    matrix[j][i] = save;
  }
}
for (int i = 0; i < 4; i++) {
  for (int j = i + 1; j < 4; j++) {
    int save = matrix[i][j];
    matrix[i][j] = matrix[j][i];
    matrix[j][i] = save;
  }
}

If it's a non-square matrix then you're SOL.

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murschech

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Re: Transpose a matrix

Feb 15th, 2005

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Originally Posted by Narue

If it's a square matrix then you can do it with something like this:
Help with Code Tags

C Syntax (Toggle Plain Text)
for (int i = 0; i < 4; i++) {
  for (int j = i + 1; j < 4; j++) {
    int save = matrix[i][j];
    matrix[i][j] = matrix[j][i];
    matrix[j][i] = save;
  }
}
for (int i = 0; i < 4; i++) { for (int j = i + 1; j < 4; j++) { int save = matrix[i][j]; matrix[i][j] = matrix[j][i]; matrix[j][i] = save; } }
If it's a non-square matrix then you're SOL.

Your program won't work. The reason is that when you write matrix[i][j] = matrix[j][i] you've lost the contents of matrix[i][j] forever and you can't get it back to put in position [[j][i]. This will do it.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
for (int i = 0; i < 4; i++)
   for (int j = 0; j < 4; j++)
    {   save = matrix[i][j];
        matrix[i][j] = matrix[j][i];
         matrix[j][i] = save;
    }
for (int i = 0; i < 4; i++)
   for (int j = 0; j < 4; j++)
    {   save = matrix[i][j];
        matrix[i][j] = matrix[j][i];
         matrix[j][i] = save;
    }

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Join Date: Dec 2004

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murschech

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Re: Transpose a matrix

Feb 15th, 2005

•

Originally Posted by Narue

If it's a square matrix then you can do it with something like this:
Help with Code Tags

C Syntax (Toggle Plain Text)
for (int i = 0; i < 4; i++) {
  for (int j = i + 1; j < 4; j++) {
    int save = matrix[i][j];
    matrix[i][j] = matrix[j][i];
    matrix[j][i] = save;
  }
}
for (int i = 0; i < 4; i++) { for (int j = i + 1; j < 4; j++) { int save = matrix[i][j]; matrix[i][j] = matrix[j][i]; matrix[j][i] = save; } }
If it's a non-square matrix then you're SOL.

Sorry. I didn't read your code carfully enough before I replied.

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Narue

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Re: Transpose a matrix

Feb 15th, 2005

>Sorry. I didn't read your code carfully enough before I replied.
Maybe you should run example code to see if it works before trying to correct it with an incorrect solution. Starting the inner loop at 0 instead of i + 1 will result in a lot of shuffling to get the same matrix that you started with, not a transposed matrix as the OP requested. So maybe you should also test your own code before posting it. Especially if you're trying to correct someone and using it as an example.

On a purely stylistic point, I have two issues with your code. First, even though it's valid the way you did it, you should always put braces around a loop or if construct that has more than a one line body. This way you don't have to rely solely on indention to prove that your code is correct. You also avoid certain pitfalls.

Second, starting the statements of a block on the same line as the opening brace is a formatting nightmare. It makes code harder to read and harder to reformat so that it's easier to follow.

Something more like this (following your apparent brace indention style):

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
for (int i = 0; i < 4; i++)
 {
   for (int j = 0; j < 4; j++)
    {
       save = matrix[i][j];
       matrix[i][j] = matrix[j][i];
       matrix[j][i] = save;
    }
 }
for (int i = 0; i < 4; i++)
 {
   for (int j = 0; j < 4; j++)
    {
       save = matrix[i][j];
       matrix[i][j] = matrix[j][i];
       matrix[j][i] = save;
    }
 }

You also failed to define save before using it, but I'll let you slide on that.

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aldrinsms

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Re: Transpose a matrix

-1

Sep 30th, 2007

How to make a program yhat make the transpose of a matrix using array and pointers C ofcourse?

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Dave Sinkula Dave Sinkula is offline

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long time no c

Re: Transpose a matrix

Sep 30th, 2007

Wonderful! Be a pompous ass and dredge up an old thread (after reiterating the same demand a 3rd time), offering nothing, and pretend you are being courteous! Well, done. *plonk*

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MANDALSHASHI MANDALSHASHI is offline

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Re: Transpose a matrix

Nov 23rd, 2008

// prog to mulltiply matrix

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include<stdio.h>
#include<conio.h>
void main()
{
int a[10][10],b[10][10],c[10][10],i,j,k,m,n,m1,n1;
clrscr();
printf("Enter array size ");
scanf("%d%d",&m,&n);
printf("Enter array size 2");
scanf("%d%d",&m1,&n1);
if(n!=m1)
{
printf("Wrong choice entered");
getch();
exit(0);
}
else
{
printf("Enter elements");
for(i=0;i<m;i++)
{
for(j=0;j<n;j++)
{
scanf("%d",&a[i][j]);
}
}
printf("Enter element 2");
for(i=0;i<m1;i++)
{
for(j=0;j<n1;j++)
{
scanf("%d",&b[i][j]);
}
}
for(i=0;i<m;i++)
{
for(j=0;j<n1;j++)
{
c[i][j]=0;
for(k=0;k<n;k++)
{
c[i][j]=c[i][j]+(a[i][k]*b[k][j]);
}
}
}
printf("REQUIRED MATRIX");
for(i=0;i<m;i++)
{
for(j=0;j<n1;j++)
{
printf("\n%d",c[i][j]);
}
printf("\n");
}
getch();
}
}
#include<stdio.h>
#include<conio.h>
void main()
{
int a[10][10],b[10][10],c[10][10],i,j,k,m,n,m1,n1;
clrscr();
printf("Enter array size ");
scanf("%d%d",&m,&n);
printf("Enter array size 2");
scanf("%d%d",&m1,&n1);
if(n!=m1)
{
printf("Wrong choice entered");
getch();
exit(0);
}
else
{
printf("Enter elements");
for(i=0;i<m;i++)
{
for(j=0;j<n;j++)
{
scanf("%d",&a[i][j]);
}
}
printf("Enter element 2");
for(i=0;i<m1;i++)
{
for(j=0;j<n1;j++)
{
scanf("%d",&b[i][j]);
}
}
for(i=0;i<m;i++)
{
for(j=0;j<n1;j++)
{
c[i][j]=0;
for(k=0;k<n;k++)
{
c[i][j]=c[i][j]+(a[i][k]*b[k][j]);
}
}
}
printf("REQUIRED MATRIX");
for(i=0;i<m;i++)
{
for(j=0;j<n1;j++)
{
printf("\n%d",c[i][j]);
}
printf("\n");
}
getch();
}
}

Last edited by Ancient Dragon; Mar 23rd, 2009 at 3:53 pm. Reason: add code tags

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Join Date: Mar 2009

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thinkammar thinkammar is offline

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Re: Transpose a matrix

Mar 23rd, 2009

Hi there
I read you method of transposing a matrix
it works
but i have toa sk a question!
that what is the logic behind initializing inner loop variable j=i+1 instead of j=0???
i shalll be thankful to you if you reply to this post
thanx