Subtract each column of matrix until -3 is finished

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Chin 2011-12-14

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https://ww2.mathworks.cn/matlabcentral/answers/23876-subtract-each-column-of-matrix-until-3-is-finished

For example, i have a matrix a = [0 1 2 3 4]. How do I subtract each column by 1?

    a = [0 3 2 6 4]
    b = [0 2 1 2 3]
    remainder = size(a, 2) - sum(b)

The remainder is -3. I need to minus from b when b(i) ~= 0 so that at the end the b = [0 1 0 1 3].

Thank you.

采纳的回答

Fangjun Jiang 2011-12-14

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https://ww2.mathworks.cn/matlabcentral/answers/23876-subtract-each-column-of-matrix-until-3-is-finished#answer_31343

在 MATLAB Online 中打开

I am curious too. Let me guess.

a=0:4;
b=-3; % b is an integer, positive or negative
c=zeros(size(a));
ind=find(a,1);
c(ind:ind+abs(b)-1)=-1;
a=a+c
a =
     0     0     1     2     4

Updated for a generic solution

b = [0 2 1 2 3]
remainder=-6;
ind=find(b);
while remainder<0 && ~isempty(ind)
    if length(ind)<=abs(remainder)
        b(ind)=b(ind)-1
        remainder=remainder+length(ind)
        ind=find(b);
    else
        for k=1:abs(remainder)
            b(ind(k))=b(ind(k))-1
            remainder=remainder+1
        end
    end
end
b =
     0     2     1     2     3
b =
     0     1     0     1     2
remainder =
    -2
b =
     0     0     0     1     2
remainder =
    -1
b =
     0     0     0     0     2
remainder =
     0

I am confused with the c and a. I suggest you ask a separate question and use variable name consistently. Also, explain the logic or step. If it's hard to explain, try to show your step and intermediate result if you do it manually, like using a pencil and a piece of paper.

Chin 2011-12-16