Insert specific number of rows of zeroes(5) after every 56 rows in my n*m matrix. I am able to create matrices but can I do the insertion without loop given I know the size of matrix? Thanks for help

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Siddhartha Sharma 2018-3-22

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评论： Siddhartha Sharma 2018-3-23

I have a huge 2464 * 2484 matrix that I want to manipulate and make 2684*2684 but I need the new 220 rows to be divided into 5 rows after every 56 rows of original matrix. I am able to think of loop code --

>> A=csvread('InputWIODRaw.csv');  
>> A=csvread('InputWIODRaw.csv');  
>> B= zeros(5,2684);  
>> CountryVar = [56:56:2464];  
>> for i = 1:44  
 if i==1
 j=1;
  elseif i>1
  j=CountryVar(i-1)+1;
 end
 ReorderMatrix(i)= A(j:CountryVar(i),:);
Reorder(i) = [ReorderMatrix(i); B];
end
error: =: nonconformant arguments (op1 is 1x1, op2 is 56x2684)
>> for i = 1:44
 if i==1
 j=1;
  elseif i>1
  j=CountryVar(i-1)+1;
 end
 ReorderMatrix(i) = zeros(56,2684);,2684)= A(j:CountryVar(i),:);
parse error:
    syntax error
>>>  ReorderMatrix(i) = zeros(56,2684);,2684)= A(j:CountryVar(i),:);
                                            ^
>> ReorderMatrix(i) = zeros(56,2684);
error: =: nonconformant arguments (op1 is 1x1, op2 is 56x2684)

But not sure how to initialize. Is there a better way if not how to rectify this code? Much appreciated

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Answer 1

Kelly Kearney 2018-3-22

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Another approach, which works even if your data doesn't divide evenly:

x = rand(21,6);
nrow = 5;    % number of rows of data in each group
nlines = 2;  % number of rows of 0s to add after each group
nsets = floor(size(x,1)./nrow);
nextra = rem(size(x,1), nrow);
x = mat2cell(x, [ones(nsets,1)*nrow; nextra], size(x,2));
x = cellfun(@(x) [x; zeros(nlines, size(x,2))], x, 'uni', 0);
x = cat(1, x{:});

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Answer 2

Guillaume 2018-3-22

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You can indeed do it without a loop.

transpose the matrix so that your rows are columns (since matlab works by column)
reshape the matrix so that each group of your original 56 rows are now a single column. Thus you end up with a matrix of 44 columns
vertically concatenate this reshaped matrix with a zero matrix of height 5*width of original matrix and of width 44
reshape the result back into the right number of rows and columns and transpose back

A = csvread('InputWIODRaw.csv');
B = A.';   
B = reshape(B, 56*size(A, 2), []);  
B = [B; zeros(5*size(A, 1), size(B, 2))];
B = reshape(B, size(A, 2), []);
B = B.';

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Siddhartha Sharma 2018-3-23

Thanks Guillaume, Although due to some reason the reshape size is throwing errors and the reverse transpose is not happening so I end up with 16800 columns.

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