Making Cumulative Difference Calculation

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Aadil
Aadil 2012-8-16
Hi,
I have a parameter with a column of data like this:
RunTime:
3779024.8; 3779025.8; 3779026.8; 3779027.8; 3779028.8; 3779029.8;
I want to know how I can make another parameter which calculates the cumulative difference between the values and presents it like this:
Elapsed Time:
0; 1; 2; 3; 4; 5; 6;
Thanks,

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José-Luis
José-Luis 2012-8-16
Not entirely sure if that's what you meant but here goes:
data = sort(rand(10,1));
cumDiff = [0;cumsum(diff(data))];
Cheers!
  2 个评论
Friedrich
Friedrich 2012-8-16
编辑：Friedrich 2012-8-16
Small note:
The perfomance of this pretty bad and it doesnt make any sense doing it like this. Simply subtract the first value from all others (assuming data is sorted ascending). This is approx. 20-30 times faster and give the exact same result.
>> data = (1:1000)';
>> tic,cumDiff = [0;cumsum(diff(data))];toc
Elapsed time is 0.000560 seconds.
>> tic,cumDiff = [0;cumsum(diff(data))];toc
Elapsed time is 0.000549 seconds.
>> tic,cumDiff = [0;cumsum(diff(data))];toc
Elapsed time is 0.000611 seconds.
>> tic,cumDiff = data-data(1);toc
Elapsed time is 0.000021 seconds.
>> tic,cumDiff = data-data(1);toc
Elapsed time is 0.000024 seconds.
>> tic,cumDiff = data-data(1);toc
Elapsed time is 0.000023 seconds.
>> tic,cumDiff = data-data(1);toc
Elapsed time is 0.000024 seconds.
José-Luis
José-Luis 2012-8-17
You are right. I guess i was blinded by the wording of the question.
Cheers!

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更多回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2012-8-16
编辑：Azzi Abdelmalek 2012-8-16
A=[3779024.8; 3779025.8; 3779026.8; 3779027.8; 3779028.8; 3779029.8];
result=[0 ;cumsum(diff(A))];
disp('elapsed time');disp(sprintf('%d;',result))

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