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'How to' Matrix

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Hello kity
Hello kity on 12 Dec 2012
Closed: MATLAB Answer Bot on 20 Aug 2021
I have an array with 0 s and 1s.
Example a colomn, 0 ,0 ,0 ,0 , 1.
Now the 1 is on the 5th row, I want to raise that to the first row.
So, in my code i want all the ones to go 4 steps up...
sounds easy, but how :) ?
  5 Comments
Hello kity
Hello kity on 12 Dec 2012
I meant shifting, shifting the 1 on the 4th row to the 1st.
Jan
Jan on 12 Dec 2012
Thanks for the clarification, Student. And what happens on the right margin? Is the result shorter, filled with zeros or ones or with the value of the last element?

Answers (4)

Walter Roberson
Walter Roberson on 12 Dec 2012
Edited: Walter Roberson on 12 Dec 2012
Have you considered circshift() up by 4 rows?

Azzi Abdelmalek
Azzi Abdelmalek on 12 Dec 2012
A=[0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 1]
for k=5:length(A)
if A(k)
b=A(k-4:k-1);
A(k-4)=1
A(k-4+1:k)=b
end
end
  2 Comments
Hello kity
Hello kity on 12 Dec 2012
Would you comment this code step by step, I dont get how you do this...
thank you
Azzi Abdelmalek
Azzi Abdelmalek on 12 Dec 2012
A=[0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 1]
for k=5:length(A)
if A(k) % If A(k) is equal to 1
b=A(k-4:k-1); % store value from k-4 to k-1 in b
A(k-4)=1 % replace value at k-1 by 1
A(k-4+1:k)=b % shift value stored in b
end
end

Andrei Bobrov
Andrei Bobrov on 12 Dec 2012
Edited: Andrei Bobrov on 12 Dec 2012
other way:
a - your vector - row (eg: [0 0 0 0 1])
n = numel(a);
out = a(hankel(1:n,[n,1:n-1]));
or
out = hankel(a,circshift(a,[0 1]));
  1 Comment
Hello kity
Hello kity on 12 Dec 2012
thank you,
afterwards i use Q=out(:,5);

Jan
Jan on 12 Dec 2012
Edited: Jan on 12 Dec 2012
Some ideas:
x = [0, 0, 0, 0, 1];
index = find(x, 1, 'first');
y1 = x(index:end);
y2 = [x(index:end), zeros(1, index - 1)];
y3 = [x(index:end), ones(1, index - 1)];
y4 = [x(index:end), repmat(x(end), 1, index - 1)];
y5 = [x(index:end), x(1:index - 1)];

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