Make function reset for every interval/day

Question

Helena Hjørringgaard 2020-4-1

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https://ww2.mathworks.cn/matlabcentral/answers/514526-make-function-reset-for-every-interval-day

回答： Deepak 2024-11-14，10:21

Hello,

I'm trying to make a loop where I want my function to reset it's calculation for every day. My array is sectioned into minutes.

So far I've made an array containing all index for every values my function needs to do it's calculation for e.g.:

di = [1 1 1 2 2 2 3 3 3 ] which corresponds to the three first days for three minutes. So I have every number repeating 60*24 times. I've used the unique function for creating this.

I have another array called t which is simply just values from a previous calculation.

First I want a function x = t*2 and I want it to reset this for each day, so every time a value in di changes.

Then I want it to cummulate all values in x for each time di changes it's value (1,2,3 ect.).

I know some have asked for similar questions (sorry) , but I cannot get their solutions to work.

I'm using Matlab2019a.

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Answer 1

Deepak 2024-11-14，10:21

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Hi @Helena Hjørringgaard,

As I understand, the task is to perform and accumulate daily calculations on minute-by-minute time-series data without overwriting previous results.

To achieve this, first use the “unique” function to identify all the unique days in “di”. Then, loop through each unique day and use logical indexing to extract the corresponding values from the t array. For each day, calculate the desired function, such as multiplying the values by 2, and then compute the cumulative sum of these results.

Here is the sample MATLAB code to achieve the same:

di = [1 1 1 2 2 2 3 3 3]; 
t = rand(size(di)); % Example array 't' with random values 
% Find unique days 
unique_days = unique(di); 
% Initialize array to store cumulative results for each day 
cumulative_results = zeros(size(unique_days)); 
for i = 1:length(unique_days) 
    day = unique_days(i); 
    
    % Find indices corresponding to the current day 
    indices = (di == day); 
    
    x = t(indices) * 2; 
    
    cumulative_results(i) = sum(x); 
end 
disp('Cumulative results for each day:'); 
disp(cumulative_results); 