find frequency and duration of numerical events in a matrix

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elisabetta fedeli 2019-3-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/448374-find-frequency-and-duration-of-numerical-events-in-a-matrix

编辑： Andrei Bobrov 2019-3-7

I have a matrix where the rows are minutes of a day (starting from 0:00 and ending at 23:59) and the columns are different days (over 1000 days). The numerical values in the matrix are events that occur over several minutes in a day so they are groups of values that extend over some rows in the same column surrounder by zeros. I would like to know, for every hour (es from 0:00 to 1:00) the mean value of the number of events that occurred and their mean duration in minutes.

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elisabetta fedeli 2019-3-5

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ok, sorry, a matrix like this but with 1440 rows, one for each minute (even if i would like to group the results by hour), and over 1000 columns. Thank you!

50	0.08	0.50	0.00	0.00	0.28	0.23	0.00
00	0.00	0.50	0.00	0.00	0.50	0.50	0.00
29	0.00	0.39	0.22	0.00	0.50	0.50	0.00
50	0.23	0.22	0.50	0.42	0.50	0.50	0.00
50	0.50	0.50	0.50	0.50	0.50	0.50	0.00
50	0.50	0.50	0.50	0.50	0.23	0.28	0.00
50	0.50	0.50	0.50	0.50	0.00	0.00	0.00
22	0.50	0.50	0.29	0.50	0.48	0.00	0.00
00	0.28	0.29	0.00	0.09	0.50	0.50	0.00
00	0.04	0.00	0.00	0.00	0.50	0.50	0.00
36	0.50	0.37	0.39	0.43	0.50	0.50	0.00
50	0.50	0.50	0.50	0.50	0.50	0.50	0.00
50	0.50	0.50	0.50	0.50	0.03	0.50	0.00
50	0.50	0.50	0.50	0.50	0.00	0.01	0.00
50	0.47	0.50	0.50	0.50	0.10	0.00	0.00
15	0.00	0.14	0.12	0.08	0.50	0.50	0.00
00	0.00	0.38	0.00	0.00	0.50	0.50	0.00
28	0.36	0.50	0.32	0.37	0.50	0.50	0.00
50	0.50	0.50	0.50	0.50	0.50	0.50	0.00
50	0.50	0.50	0.50	0.50	0.41	0.50	0.00
50	0.50	0.50	0.50	0.50	0.21	0.01	0.00
50	0.50	0.13	0.50	0.50	0.50	0.00	0.00
23	0.15	0.00	0.19	0.14	0.50	0.19	0.00
00	0.06	0.43	0.05	0.16	0.50	0.50	0.00
00	0.50	0.50	0.50	0.50	0.50	0.50	0.00
04	0.50	0.50	0.50	0.50	0.30	0.50	0.00
50	0.50	0.50	0.50	0.50	0.00	0.50	0.00
50	0.50	0.50	0.50	0.50	0.46	0.32	0.00
50	0.45	0.08	0.46	0.35	0.50	0.00	0.00
50	0.00	0.30	0.00	0.00	0.50	0.48	0.00

dpb 2019-3-5

在 MATLAB Online 中打开

OK, so we are clear on the definition of "event'...for the first column

50
00
29  -- begin?
50            or --begin?
50
50
50
22              -- end?
00  -- end??
00
...

is the event the any stretch of nonzero values or the stretch of equi-valued values?

Is the duration of the even inclusive/exclusive of the start/stop markers on one/both/either end?

elisabetta fedeli 2019-3-6

在 MATLAB Online 中打开

Thank you for the reply, the event is any stretch of nonzero values.

50  -- begin and end (duration 1 minute)
00
29  -- begin
50          
50
50
50
22  -- end (duration 6 minutes)
00  
00
...

It would also be ideal if I could consider an event overlapping 2 hours a fraction of an event. Like this:

50  -- begin and end (duration 1 minute)
00
29  -- begin
50  --- end (the event is considered 2/6 of an event, duration 2 minutes)    
----------- end of the first hour (every hour is composed of 60 rows)
50  --- begin
50
50
22  -- end (the event is considered 4/6 of an event, duration 4 minutes)
00  
00
...

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Answer 1

Andrei Bobrov 2019-3-6

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/448374-find-frequency-and-duration-of-numerical-events-in-a-matrix#answer_364055

编辑：Andrei Bobrov 2019-3-7

在 MATLAB Online 中打开

Let A - your array (1440 x Days):

k = 60;% k = 60 (minuties in hour)
[m,n] = size(A);
a1 = A ~= 0;
A1 = diff([false(1,n);a1]) == 1;
[ii,iii] = ndgrid(1:k,1:m/k);
A1(ii(:) == 1 & a1) = true;
data = cumsum(A1).*double(a1);
T = array2table([iii(:),data],'V',[{'Time'},sprintfc('DAY%d',1:n)]);
out = varfun(@fun,T,'InputVariables',2:n+1,'GroupingVariables',1);
out = out(:,[1,3:end]);
out.Properties.VariableNames{1} = 'Hour';

Here fun is m-file fun.m:

function y = fun(x)
    [~,~,c] = unique(x(x > 0));
    y = [max(c), mean(accumarray(c,1))];
end

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elisabetta fedeli 2019-3-6

Thank you very much! It works but i'm not sure it serves my purpose or maybe I just don't understand the script. I'm very new to matlab and i understand that every element in a column of the out matrix is an event and it's value is it's duration. Is it possible to group the results by hour? To have an out matrix 24 x n.days so that if in an hour there's no event the value for that hour is zero?