1D array values to 2D matrix

I would like to 'convert' a 1D array to a 2D matrix considering the value inside the array as:

A =

     1     3     5     4     3

B =

     1     3     5     4     3
     0     3     5     4     3
     0     3     5     4     3
     0     0     5     4     0
     0     0     5     0     0

Can you suggest a fast way to do that?

Answer 1

[Adam Danz]

A for-loop would make a cleaner read (I could provide that upon request) but here's two lines the do the trick.

base = cellfun(@(x)repmat(x,x,1), num2cell(A), 'UniformOutput', false);
cell2mat(cellfun(@(y,n) padarray(y,n, 'post'),base, num2cell(max(A)-A), 'UniformOutput', false))

ans =
     1     3     5     4     3
     0     3     5     4     3
     0     3     5     4     3
     0     0     5     4     0
     0     0     5     0     0

[Eduardo Santos]

Thanks, it worked nicely.

Just wondering.. keeping the same idea but instead to keep the number, get only the numer 1 in the cell function, like:

ans =
     1     1     1     1     1
     0     1     1     1     1
     0     1     1     1     1
     0     0     1     1     0
     0     0     1     0     0

What should I do?

[Eduardo Santos]

B(B>0)=1; ?

[Adam Danz]

Your solution above is one way to do it. If you don't need the original matrix in the first place and want to bypass that,

%                 |-------|  This is the only change
base = cellfun(@(x)ones(x,1), num2cell(A), 'UniformOutput', false);
cell2mat(cellfun(@(y,n) padarray(y,n, 'post'),base, num2cell(max(A)-A), 'UniformOutput', false))

[Eduardo Santos]

Hy Adam.

How can I change for

ans =

1 1 1 1 1

0 2 2 2 2

0 3 3 3 3

0 0 4 4 0

0 0 5 0 0

Cheers!

[Adam Danz]

A = [1,3,5,4,3]

A = 1×5

1 3 5 4 3

B = zeros(max(A),numel(A));
for i = 1:numel(A)
    B(1:A(i),i) = 1:A(i);
end
disp(B)

     1     1     1     1     1
     0     2     2     2     2
     0     3     3     3     3
     0     0     4     4     0
     0     0     5     0     0

[Eduardo Santos]

Hi Adam, thanks for the answer. I was wondering something like your previous version but it works anyway.