MATLAB: Moving window with cumulative sum less than a ref value and excluding certain windows

cumulative summoving window

I have an array of 36000 cells, i want to break those arrays into windows of cumulative sum less than a reference value. and exclude few windows based on other parameters respective to this array based on index. For example A= [ 0.5 0.6 .45 .56 .056 .16 .18 .10 .15 .45 .36]; similarly other arrays of same length. Now window 1 should start with 1st value and end at sum less than 2 ( window{1} = [0.5 0.6 .45], sum = 1.55) second window has to start from 2nd value ( window{2} = [0.6 .45 .56 .056 .16], sum = 1.826). Similarly i need all possible windows for 36000 cells, while excluding those where value/sum of other arrays/windows of respective index. Index of these windows is also needed. I here wanted a moving window. Eg Index of my windows would be like [ 1 3] , [2 6], [3 9], [4 10], [5 11], [6 11], [ 7 11], [ 8 11], [9 11], [10, 11].
  • If i don't wont to consider values in index 3,4, 8, i want to exclude windows which include these indexes.
  • If i want to exclude windows whose corresponding array average is less than certain value. Ex: I've another B whose size is same as A. after breaking array A into windows, average of array B windows is less than a value (20) has to be excluded.

Best Answer

Ranji
This is John BG <mailto:jgb2012@sky.com jgb2012@sky.com> , all together in one block
load Array.mat;
tic
A2=cumsum(A);
numA=numel(A);
n1=1;n2=1;
B=[0 0];
t0=38.19;
while n1<numA || n2<numA 
    while A(n1)==0 
        n1=n1+1;
        n2=n2+1; 
    end
    while A2(n2)-A2(n1)<t0  && n2<numA
        n2=n2+1;
        while A(n2)==0 
            n2=n2+1; 
        end
    end
    B=[B;n1 n2-1];
    n1=n1+1;
    n2=n1;
end
B(1,:)=[]
% masking
mask=[3 4 8];
d=0;
for n=mask
   for k=1:1:size(B,1)
       if intersect([B(k,1):1:B(k,2)],n)
          d=[d k];     
       end
   end
end
d(1)=[];
d=unique(d);d=sort(d);
B(d,:)=[];
reasons why I ask you to consider accepting my answer:
1. my code works, no errors like Jan Simon's Out(end,:)=[36800 36799]
2. my excluding mask section doesn't crash, like Simon's.
3. from 1.7 seconds to 0.5 seconds .. if it's really about cutting down time, C should be the language to use.
4. Ranji, If it's really about speed you may want to compile it, which will require the coder to get it all through C before building the .exe and then functions cumsum and find are going to add many more lines and end up taking more time than the few lines I have supplied.
5. the warning error that Jan Simon claims does not show up in MATLAB version R2016, it may happen in his MATLAB version R2009 but not in up to date MATLAB version.
6. his recommendation ' .. This is always a bad programming practize .. ' is the typical pointless remark that does not contribute to help solve the question.
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