# looping till a condition is met.....

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sri satya ravi on 27 Dec 2016
Commented: Image Analyst on 8 Jan 2017
Hi;
I have an array of 2400 values. I want to loop such that i need to break into chunks till the sum becomes (say for suppose 2). i want to add 1st value plus 2nd value so on till the condition is met and then after the condition is met start adding from next number again till the condition meets.
I need chunks of values whose sum is 2 and i don't know the the exact chunks which vary by the data and the limit i set for the condition to break.
limit = 2;
s = 0;
for i = 1:length(Work)
while 1
if s >= limit
break
end
s = s + Work(i);
end
W = Work(i)
end

Image Analyst on 28 Dec 2016
I believe this will do what you want. Give it a try. It scans along work getting the cumulative sum from that index onwards. Then it finds the first index where that cumulative sum exceeds 2. When that happens, it records the sum for that chunk (typically in the range 2-3) and the original index where that chunk ends.
% Create sample data.
Work = rand(2400,1);
% Define the limit of sums that the chunks need to surpass.
sumLimit = 2;
% Preallocate more memory than needed for W
sumValues = zeros(size(Work));
indexLocations = zeros(size(Work));
chunk = 1; % Index for what chunk we're working on.
index = 1;
while index < length(Work) && chunk < length(Work)
% Find the sums from this index onwards to the end of the Work vector.
cdf = cumsum(Work(index:end));
% Find the first time the sum exceeds the limit.
limitLocation = find(cdf > sumLimit, 1, 'first');
% Remember, limitLocation is relative to Index, not to element 1.
% If no remaining sum is more than sumLimit, just break out of the loop.
if isempty(limitLocation)
break;
end
% Save this sum value.
sumValues(chunk) = cdf(limitLocation);
% Save this index value. The index value relative to index 1, not relative to limitLocation.
indexLocations(chunk) = limitLocation + index - 1;
% Move pointer to the next element.
index = indexLocations(chunk) + 1;
% Increment what chunk number we're working on.
chunk = chunk + 1;
end
% Trim trailing zeros from sumValues and indexLocations.
sumValues(sumValues == 0) = []
indexLocations(indexLocations == 0) = []
Image Analyst on 8 Jan 2017
Try this:
function metCondition = CheckChunkCondition(vector)
metCondition = true; % Initialize
if any(vector < 200)
metCondition = false;
end

### More Answers (1)

the cyclist on 27 Dec 2016
Edited: the cyclist on 27 Dec 2016
Here's one way. The core idea is that one tests whether the current value of W is over the limit, and if so then move the "pointer" index to the next element.
% Some pretend data
Work = rand(2400,1);
limit = 2;
% Preallocate
W = zeros(size(Work));
C = zeros(size(Work));
idx = 1;
for i = 1:length(Work)
C(idx) = C(idx) + 1;
if W(idx) >= limit
idx = idx + 1;
end
W(idx) = W(idx) + Work(i);
end
% Trim the excess from W and C
W(idx+1:end) = [];
C(idx+1:end) = [];
the cyclist on 27 Dec 2016
I've edited the code to track that in the variable C.