Decrementing an Array

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.

[Mustafa]

Just for future reference.

The answer by "the cyclist" is also correct. Personally it suits me better.

Answer 1

[Andrei Bobrov]

?

Ds = cumsum([n;-ones(max(n),length(n))]);
Ds(Ds<0)=0

[Mustafa]

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.

Answer 2

[the cyclist]

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

[Mustafa]

Thanks, but 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.

[Jan]

not(all(n==0)) is equivalent to any(n).

[Mustafa]

Thanks a lot...works as i really want it to work. Appreciate it :)

[Mustafa]

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.

Answer 3

[Jan]

See ALL and ANY:

n=[8 5 9 3 6 11]
if all(n~=0)   % Equivalent: if all(n)
  n = n-1
end

[Mustafa]

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.

Answer 4

[Sean de Wolski]

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

[Mustafa]

Thanks, but 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.

[Sean de Wolski]

n = zeros(size(n))

[Mustafa]

Can you write the whole code, i am sorry i couldn't figure it out.

[Sean de Wolski]

Well you want to decrement every value to zero so you'll just have an array of values. Why waste the time and effort doing the math - just define it as an array of zeros.

[Sean de Wolski]

while any(~n)

n(~n) = n(~n)-1;

end

is the mathy way to do it

[Mustafa]

:).

Well i need to decrement the array till zero and if one of the element arrives at zero, i need to perform some operation and than continue to decrement the array again. The element that become zero will get a new random number after some time. It goes on like this.

But thanks anyways :)

[Bheki Ngobe]

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]

You should probably ask a new question, rather than add a comment to a 4-year-old question.