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Decrementing an Array

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Mustafa
Mustafa 2011-7-11
评论： the cyclist 2016-2-15
Hi,
I am new to Matlab and i am trying to decrement a simple array. I want every element to arrives at zero and no negative. The problem is once any element of the array arrives at zero the decrement stops, i have tried to use several combination but nothing works. It goes like this
n=[8 5 9 3 6 11]
if n~=0
n=n-1
end.
As soon as the the value '3' arrives at zero the decrement stops. I have also used "sum" but it didn't work either. For instance while sum~=0, do the decrement but it didn't work either. I know its a simple task but i am stuck.
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Mustafa
Mustafa 2011-7-11
Just for future reference.
The answer by "the cyclist" is also correct. Personally it suits me better.

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2011-7-11
?
Ds = cumsum([n;-ones(max(n),length(n))]);
Ds(Ds<0)=0
  1 个评论
Mustafa
Mustafa 2011-7-11
Thats it. Thanks a trillion.
I thought there must be simple "if" or "while" statement to do this but thats good for now.
Appreciate it.
P.S: Is there any way to stop the decrement once i found that one elment of the array arrives at zero. I need to perform some operation and than continue with the decrement.

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更多回答（3 个）

the cyclist
the cyclist 2011-7-11
Edited in response to your comment:
while not(all(n==0))
n = max(0,n-1)
end
Wanted to keep this all in one answer. I have edited my response again, but left the old one. In the code below, I have inserted an if statement that will be entered only when an element of n has just been decremented to zero, as you mentioned you wanted in a comment on andrei's answer.
(I also implemented Jan's simpler syntax for the while loop.)
n0 = [8 5 9 3 6 11];
n = n0;
iter = 0;
while any(n)
iter = iter+1;
n = max(0,n-1)
if any(iter==n0);
% If I am here, it is because one of the original element just reached zero
% Do stuff
end
end
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Mustafa
Mustafa 2011-7-11
Thanks a lot...works as i really want it to work. Appreciate it :)
Mustafa
Mustafa 2011-7-12
Thanks again for help. Really appreciate it. Well in my case i have to assign the " particular element" that become zero another value. I have done it like this
for i=1:40 % Just a loop so that the iteration will keep on running
while any(n)
n=max(0,n-1)
n_indx=find(n==0)
n(n_indx)=20 % Let say i have to assign that element a value of 20.
break
end
end
There is problem if you run the above code, the decrement happens after every second step. Please check the output to understand it more clearly.

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Jan
Jan 2011-7-11
See ALL and ANY:
n=[8 5 9 3 6 11]
if all(n~=0) % Equivalent: if all(n)
n = n-1
end
  1 个评论
Mustafa
Mustafa 2011-7-11
Your code stops after two iterations,
I want every element of the array to arrives at zero. If let say "3" becomes zero in third iteration, it will remain zero until "11" arrives at zero.

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Sean de Wolski
Sean de Wolski 2011-7-11
n = n-min(n(:));
?
And the way to fix your if statement is to use any as the criterion.
while ~any(n==0)
n = n-1;
end
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Bheki Ngobe
Bheki Ngobe 2016-2-14
Hi
I have kind of similar problem but I am using 3x4 array. How should I do it in this situation. In brief I want to apply an formula in each cell and increment to the next one until all cells are updated. Please help
the cyclist
the cyclist 2016-2-15
You should probably ask a new question, rather than add a comment to a 4-year-old question.

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