Increment dates using for loop

Question

CM 2019-2-9

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/443993-increment-dates-using-for-loop

回答： Stephen23 2019-2-9

I'm trying to fill a variable sized datetime array. I then want the declared datetime value to fill the first 3 elements before incrementing by one to fill the next three.This process repeats until the desired sized element is reach. See current output & desired output.

Code:

samples = input("Number of Samples to Generate: ");
DateBuilt = repmat(datetime(0,0,0),samples,1);
t = datetime(2018,1,1);
DateBuilt(1) = t 
for i=1:samples
        if i <= 3
            DateBuilt(i) = t; 
        else
            t = t + 1;
            DateBuilt(i) = t;
end   

Current Output:

Number of Samples to Generate: 14
DateBuilt = 
  14×1 datetime array
   01-Jan-2018 
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001
   30-Nov--0001

Desired Output:

   Number of Samples to Generate: 14
DateBuilt = 
  14×1 datetime array
   01-Jan-2018 
   01-Jan-2018
   01-Jan-2018
   02-Jan-2018
   02-Jan-2018
   02-Jan-2018
   03-Jan-2018
   03-Jan-2018
   03-Jan-2018
   04-Jan-2018
   04-Jan-2018
   04-Jan-2018
   05-Jan-2018
   05-Jan-2018

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madhan ravi 2019-2-9

编辑：madhan ravi 2019-2-9

Why in your desired output the last date has only repeated twice , any reason for it?

CM 2019-2-9

Yes. The user input (*see “samples“ variable in code) determines the number of elements in the datetime array. The first element of array is filled with a datetime. The loop then continues to fill the 2nd and 3rd elements before incrementing by 1 day. the loop then proceeds to fill the 4th, 5th, and 6th elements before incrementing again and repeating the process for the next three elements This continues until the user defined size is reached. Repeating the last date only twice is my attempt to show that the loop stops based on an arbitrary number entered by the user.

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Answer 1

Eric Sofen 2019-2-9

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Are there any other calculations being done in the loop body of your actual code? If not, this can be done without looping:

samples = input("Number of Samples to Generate: ");
days = floor((0:samples-1)./3)'+1;
dt = datetime(2018,1,days);

If you do really need to loop for some other reason, there are things that need to change in your code:

1) It's missing and end to the conditional block.

2) t = t+1 ends up incrementing the day every iteration.

samples = input("Number of Samples to Generate: ");
DateBuilt = repmat(datetime(0,0,0),samples,1);
t = datetime(2018,1,1);
DateBuilt(1) = t;
for i=1:samples
    DateBuilt(i) = t+days(floor((i-1)/3));
end   

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Answer 2

Stephen23 2019-2-9

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/443993-increment-dates-using-for-loop#answer_360234

>> D = datetime('01-Jan-2018');
>> N = 14;
>> G = 3;
>> V = D + caldays(0:ceil(N/G)-1).';
>> V = repelem(V,G);
>> V = V(1:N)
V = 
   01-Jan-2018
   01-Jan-2018
   01-Jan-2018
   02-Jan-2018
   02-Jan-2018
   02-Jan-2018
   03-Jan-2018
   03-Jan-2018
   03-Jan-2018
   04-Jan-2018
   04-Jan-2018
   04-Jan-2018
   05-Jan-2018
   05-Jan-2018