resize a matrix and missed data "zero"

Question

sia ben 2022-4-9

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https://ww2.mathworks.cn/matlabcentral/answers/1692665-resize-a-matrix-and-missed-data-zero

编辑： MJFcoNaN 2022-4-9

Hi! I have a data which are is like:

[1 2 5; 80 50 60], [1 3 4; 40 65 23], ...and i want to change all of them to [1 2 3 4 5;80 50 0 0 60], [1 2 3 4 5; 40 0 65 23 0] without loop. It means first row for all shuld be numbers 1-5 and the second row the related number and for not existing data a zero. how is it possible?

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Answer 1

Voss 2022-4-9

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% first matrix:
A = [1 2 5; 80 50 60];
% these two lines of code work for a single matrix:
new_A = [1:5; zeros(1,5)];
new_A(2,A(1,:)) = A(2,:)
new_A = 2×5
     1     2     3     4     5
    80    50     0     0    60
% second matrix:
A = [1 3 4; 40 65 23];
% same two lines of code as above:
new_A = [1:5; zeros(1,5)];
new_A(2,A(1,:)) = A(2,:)
new_A = 2×5
     1     2     3     4     5
    40     0    65    23     0
% alternatively, a cell array of all your matrices:
A = {[1 2 5; 80 50 60]; [1 3 4; 40 65 23]};
% put those two lines of code in a function and 
% use cellfun to apply it to all the matrices:
new_A = cellfun(@expand_matrix,A,'UniformOutput',false)
new_A = 2×1 cell array
    {2×5 double}
    {2×5 double}
new_A{:}
ans = 2×5
     1     2     3     4     5
    80    50     0     0    60
ans = 2×5
     1     2     3     4     5
    40     0    65    23     0
function new_A = expand_matrix(A)
new_A = [1:5; zeros(1,5)];
new_A(2,A(1,:)) = A(2,:);
end

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Answer 2

the cyclist 2022-4-9

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Here is one way:

M = [ 1  2  5;
     80 50 60];
Mrange = M(1,1):M(1,end);
Mexpanded = [Mrange; zeros(1,M(1,end))];
Mexpanded(:,M(1,:)) = M
Mexpanded = 2×5
     1     2     3     4     5
    80    50     0     0    60

It might make some assumptions based on the two example you gave (which both started with 1, and are sorted, for example). You might need to generalize, if you have cases that look different.