Subtract each column of matrix until -3 is finished
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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.
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Fangjun Jiang
2011년 12월 14일
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
댓글 수: 9
Fangjun Jiang
2011년 12월 16일
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.
추가 답변 (1개)
Walter Roberson
2011년 12월 14일
Does the minus sign of -3 indicate the third from the start or the third from the end? Your example is ambiguous about that.
Third from the start:
a(1:abs(b)) = a(1:abs(b)) - 1;
Third from the end:
a(1:end-abs(b)+1) = a(1:end-abs(b)+1) - 1;
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