How to extract a 2x2 submatrix from a bigger matrix
- by ZaZu
Hello,
I am a very basic user and do not know much about commands used in C, so please bear with me...I cant use very complicated codes. I have some knowledge in the stdio.h and ctype.h library, but thats about it.
I have a matrix in a txt file and I want to load the matrix based on my input of number of rows and columns
For example, I have a 5 by 5 matrix in the file. I want to extract a specific 2 by 2 submatrix, how can I do that ?
I created a nested loop using :
FILE *sample
sample=fopen("randomfile.txt","r");
for(i=0;i<rows;i++){
for(j=0;j<cols;j++){
fscanf(sample,"%f",&matrix[i][j]);
}
fscanf(sample,"\n",&matrix[i][j]);
}
fclose(sample);
Sadly the code does not work .. If I have this matrix :
5.00 4.00 5.00 6.00
5.00 4.00 3.00 25.00
5.00 3.00 4.00 23.00
5.00 2.00 352.00 6.00
And inputting 3 for row and 3 for column, I get :
5.00 4.00 5.00
6.00 5.00 4.00
3.00 25.00 5.00
Not only this isnt a 2 by 2 submatrix, but even if I wanted the first 3 rows and first 3 columns, its not printing it correctly....
I need to start at row 3 and col 3, then take the 2 by 2 submatrix !
I should have ended up with :
4.00 23.00
352.00 6.00
I heard that I can use fgets and sscanf to accomplish this. Here is my trial code :
fgets(garbage,1,fin);
sscanf(garbage,"\n");
But this doesnt work either :(
What am I doing wrong ?
Please help.
Thanks !
