Need to split matrix(m x n) where n varies

Hello everyone,

I have read a lot about splitting matrices and have come close to my intended output but I'm still not there. My matrix is size (7745 x 13 double) and I would like to create 2 new datasets. The number of datasets produced will vary depending on the number of columns in the matrix(which will depend on the number of objects imported):

               7 cols = 1 dataset
               13 cols = 2 datasets
               19 cols = 3 datasets
               etc...

Each dataset needs to have 7 cols of data(the 1st col will be reproduced in each dataset followed by the next 6 cols):

               Dataset 1 = matrix(cols_1-7
               Dataset 2 = matrix(col_1, cols_8-13)
               Dataset 3 = matrix(col_1, cols_14-19)
               etc...

Given that the matrix dimension 'n' will vary by a value of 6 depending on the number of objects imported I would like the code to be dynamic. I know I can do this interactively but I will also be working with big data and would like a programatic solution.I am not sure if this is possible, efficient or otherwise. I will need to access each column individually and know what "group" of 7 vectors it belongs to, thats why I am thinking datasets, maybe struct would be better.

Thanks for you help,

Please let me know if I can provide any other info to help with the solution.

Answer 1

[Azzi Abdelmalek]

M=rand(7745,13);
[n,m]=size(M);
m=m-1;
c1=M(:,1);
mm=fix(m/6)*6;
m1=m-mm;
M(:,end+1:end+mod(6-m1,6))=nan;
A=M(:,2:end);
B=reshape(A,n,6,[]);
[n,m,p]=size(B);
out=zeros(n,m+1,p);
for k=1:size(B,3)
  out(:,:,k)=[c1 B(:,:,k)];
end

[rewayda mohsin]

Dear Azzi,

i used your code for this matrix

M=[ 1     0     1     1     0     0     0     0     0    0
    0     0     0     0     0     0     1     1     1    1
    0     1     1     1     0     0     0     0     0    0
    0     0     0     0     0     0     0     0     0    0
    0     0     0     0     1     0     0     0     0    0
    0     0     1     1     0     0     0     0     0    0
    1     0     1     1     0     0     0     0     0    0
    0     0     0     0     1     1     1     0     0    0];
 [n,m]=size(M);
mm=fix(m/5);
m1=m-mm;
M(:,end+1:end+mod(2-m1,2))=nan;
A=M(:,1:end);
B=reshape(A,n,5,[]);
[n,m,p]=size(B);
out=zeros(n,m,p);
for k=1:size(B,3)   % must be more than 3 to get just two matrices
out(:,:,k)=[B(:,:,k)]
end

I need to get just the two matrices out(:,:,1) ,out(:,:,2) but I got many. I just need the final two matrices, could you please help me with it. thanks for the code.

regards,

reway

[Steven Lord]

The statement inside the FOR loop does not end in a semicolon, so the "many" outputs you're seeing are the out array being displayed at each iteration. Add the semicolon to the "out(:, :, k) = ..." line, then display the variable named out after the FOR loop is complete.

[rewayda mohsin]

Thanks Steven,

how I didn't notice that.

many thanks

Answer 2

[Justin]

 Thanks for the quick response.  How can I maintain number formatting? See below.

Sample Desired Output (Dataset 1):

    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3477e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3478e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3478e+005       NaN       NaN       NaN       NaN      NaN      NaN
    7.3478e+005    101.85    102.75    100.78    101.71     1000      742
    7.3478e+005    101.16    102.28     99.17     99.79      976      736
    7.3478e+005    101.95     102.8     100.8    102.73      539      736
    7.3478e+005     103.3    105.84    101.59    105.73      706      732
    7.3478e+005     105.4    106.55    104.41    105.88      699      791

Same Sample Using the code provided:

    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3477       NaN       NaN       NaN       NaN       NaN       NaN
    7.3478       NaN       NaN       NaN       NaN       NaN       NaN
    7.3478    0.0010    0.0010    0.0010    0.0010    0.0100    0.0074
    7.3478    0.0010    0.0010    0.0010    0.0010    0.0098    0.0074
    7.3478    0.0010    0.0010    0.0010    0.0010    0.0054    0.0074
    7.3478    0.0010    0.0011    0.0010    0.0011    0.0071    0.0073
    7.3478    0.0011    0.0011    0.0010    0.0011    0.0070    0.0079

[Justin]

I found I can redefine 'out' into new variables and the number formatting returns.

Thanks again.