Remove leading zeros from dates strings

Question

Santiago Costantino 2020-7-16

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https://ww2.mathworks.cn/matlabcentral/answers/566106-remove-leading-zeros-from-dates-strings

评论： Santiago Costantino 2020-7-17

Hello

I need to find the number of times a set of dates is included in a large text file. The problem is that the text file does not use leading zeros for months and days.

My code should look something like this:

myText=fileread('largeFile.txt');
dayOne=datetime('06/05/20','InputFormat','MM/dd/yy')
for it=1:10
    numberOfTimes(it)=size(regexp(myText, datestr(dayOne+days(it), 'mm/dd/yy')), 2);
end

Thanks

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jonas 2020-7-16

编辑：jonas 2020-7-16

Why not simply count the dates with hist?

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Answer 1

jonas 2020-7-16

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You can use histogram() to count occurences, either with datetime or categoricals as input.

dates = datetime(2010,1,12) + rand(1000,1)*days(365);
% with categoricals
dates_cell = cellstr(datestr(dates,'mm/dd/yy'));
dates_cat = categorical(dates_cell);
H = histogram(dates_cat)

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Walter Roberson 2020-7-17

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You could use mm and then use regexp to strip out leading 0. But it hardly seems worth it considering that datetime() can handle the situation

dates = datetime(2010,1,12) + rand(10,1)*days(365);
dates.Format = 'M/d/yy';
dates_cat = categorical(cellstr(dates));
histogram(dates_cat);

Santiago Costantino 2020-7-17

That does it. Thank you, Walter.

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Answer 2

Steven Lord 2020-7-16

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Use M instead of MM and d instead of dd in the input format. According to the description of the Format property on the documentation page (which is referenced in the documentation for 'InputFormat'), M handles "Month, numerical using one or two digits" as opposed to MM which handles "Month, numerical using two digits".

>> datetime('07-16-2020', 'InputFormat', 'M-dd-yyyy')
ans = 
  datetime
   16-Jul-2020
>> datetime('7-16-2020', 'InputFormat', 'M-dd-yyyy')
ans = 
  datetime
   16-Jul-2020

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Santiago Costantino 2020-7-16

编辑：Santiago Costantino 2020-7-16

Sorry, I guess my question was not clear enough.

The dates in the text file are written as '4/7/20' for April 7th 2020. I need to find the number of occurrences of each one of many different and consecutive dates in the text.

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