Saving multiple single vectors in one Matlab file

Hi,

I need your help:

Here's a simple example:

A = magic(3);                     
B = padarray(A,[1 1]);                
[row, col] = size(B);  
for i = 2:row-1                                            
    for j = 2:col-1           
        C = [B(i-1,j-1),B(i-1,j),B(i-1,j+1),B(i,j-1),B(i,j),B(i,j+1),B(i+1,j-1),B(i+1,j),B(i+1,j+1)]           
        save C.mat
    end
end

When you run the above code in Matlab, you will get the following output in the command window

C = 0     0     0     0     8     1     0     3     5

C = 0     0     0     8     1     6     3     5     7

C = 0     0     0     1     6     0     5     7     0

C = 0     8     1     0     3     5     0     4     9

C = 8     1     6     3     5     7     4     9     2

C = 1     6     0     5     7     0     9     2     0

C = 0     3     5     0     4     9     0     0     0

C = 3     5     7     4     9     2     0     0     0

C = 5     7     0     9     2     0     0     0     0

I would like to save the following output in C.mat file using "save" function

0     0     0     0     8     1     0     3     5

0     0     0     8     1     6     3     5     7

0     0     0     1     6     0     5     7     0

0     8     1     0     3     5     0     4     9

8     1     6     3     5     7     4     9     2

1     6     0     5     7     0     9     2     0

0     3     5     0     4     9     0     0     0

3     5     7     4     9     2     0     0     0

5     7     0     9     2     0     0     0     0

However, when I use "save" C.mat, I can only output and save one line, shown below.

5     7     0     9     2     0     0     0     0

Can you help to correct the above code to be able to save the above 9-by-9 matrix in C.mat file?

Answer 1

[Cris LaPierre]

You overwrite your variable C in each loop, and you overwrite C.mat as well, so the final contents are just what was created in the last loop. I would do something like the following to append the result of each loop to C rather than replace.

A = magic(3);                     
B = padarray(A,[1 1]);                
[row, col] = size(B);  
C = [];
for i = 2:row-1                                            
    for j = 2:col-1           
        C = [C;B(i-1,j-1),B(i-1,j),B(i-1,j+1),B(i,j-1),B(i,j),B(i,j+1),B(i+1,j-1),B(i+1,j),B(i+1,j+1)];
    end
end
C

C = 9×9

0 0 0 0 8 1 0 3 5 0 0 0 8 1 6 3 5 7 0 0 0 1 6 0 5 7 0 0 8 1 0 3 5 0 4 9 8 1 6 3 5 7 4 9 2 1 6 0 5 7 0 9 2 0 0 3 5 0 4 9 0 0 0 3 5 7 4 9 2 0 0 0 5 7 0 9 2 0 0 0 0

save C.mat

% Check that C.mat contains all 9 values
clear
load C.mat
C

C = 9×9

0 0 0 0 8 1 0 3 5 0 0 0 8 1 6 3 5 7 0 0 0 1 6 0 5 7 0 0 8 1 0 3 5 0 4 9 8 1 6 3 5 7 4 9 2 1 6 0 5 7 0 9 2 0 0 3 5 0 4 9 0 0 0 3 5 7 4 9 2 0 0 0 5 7 0 9 2 0 0 0 0

[Gobert]

Thank you! It works!

[Gobert]

@Cris LaPierre

There is a little concern about the above code. I notice that it saves everything. For example, for example, when I used A = magic(5), and loaded the C.mat file, I got the below output. Of course, I can use X.C to only access the content of C. However, I do not want my .mat file to contain other details other than those in C. Therefore, can you please suggest modifications to your code to only single out and SAVE the content of C?

X = load('C.mat')

X = 

struct with fields:

A: [5×5 double]
B: [7×7 double]
C: [25×9 double]
col: 7
i: 6
j: 6
row: 7

[Cris LaPierre]

There are multiple syntaxes you can use when calling save. Check out the documentation page to learn about each. The one you want is

save(filename,variables)