Asked by Hello kity
on 12 Dec 2012

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 :) ?

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Answer by Walter Roberson
on 12 Dec 2012

Edited by Walter Roberson
on 12 Dec 2012

Have you considered circshift() up by 4 rows?

Answer by 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

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
on 12 Dec 2012

Answer by Andrei Bobrov
on 12 Dec 2012

Edited by 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]));

Answer by Jan Simon
on 12 Dec 2012

Edited by Jan Simon
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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## 5 Comments

## Walter Roberson (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/56371#comment_116684

What if there is a 1 in the first 4 columns?

Also, should the new matrix have fewer columns?

## TAB (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/56371#comment_116685

Then what should be left in 5th column (or row in your words) ?

## Jan Simon (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/56371#comment_116704

@Student: The question remains, what "raise to the first row" exactly means. At first I guess it is the "first column", but "raising" can be swapping, shifting, circular shifting, sorting, cropping or any procedure I cannot imagine currently.

## Hello kity (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/56371#comment_116710

I meant shifting, shifting the 1 on the 4th row to the 1st.

## Jan Simon (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/56371#comment_116721

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?