Read CSV with yyyyMMddhhmmss and group months

Question

Lauren 2022-1-9

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https://ww2.mathworks.cn/matlabcentral/answers/1625270-read-csv-with-yyyymmddhhmmss-and-group-months

评论： Lauren 2022-1-12

Hello! Matlab newbie, so I apologize if this is a simple question.

I've got a 5000 by 1 CSV file filled with numbers in the yyyyMMddhhmmss format. I'm simply trying to group each line by month.

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Stephen23 2022-1-10

编辑：Stephen23 2022-1-10

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@Lauren: what version of MATLAB are you using?

" I'm simply trying to group each line by month."

Which of these to you want?:

group by month only (so you will get twelve groups, i.e. 2021-03 is in the same group as 2019-03)
group by month of every year (i.e. 2021-03 is in a different group from 2019-03).

What do you want to occur with missing data? For example, such as here:

Note that your description does not match the uploaded file:

yyyyMMddhhmmss % your description.
202009090029   % actually in the file (no seconds).

Lauren 2022-1-11

Great points. I want your option 1: to group by month so there are 12 groups.

Yes, you are correct. There are not seconds. It shoulud be yyyyMMddhhmm. Mea Culpa!

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Answer 1

Stephen23 2022-1-11

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https://ww2.mathworks.cn/matlabcentral/answers/1625270-read-csv-with-yyyymmddhhmmss-and-group-months#answer_872780

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sample.csv

Here is one way to group by month only, ignoring empty lines of the CSV file:

str = fileread('sample.csv');
tkn = regexp(str,'^(\d{4})(\d\d)','tokens','lineanchors');
tkn = vertcat(tkn{:})
tkn = 5091×2 cell array
    {'2020'}    {'09'}
    {'2020'}    {'09'}
    {'2019'}    {'08'}
    {'2019'}    {'03'}
    {'2019'}    {'02'}
    {'2020'}    {'06'}
    {'2019'}    {'03'}
    {'2020'}    {'06'}
    {'2020'}    {'06'}
    {'2020'}    {'06'}
    {'2020'}    {'06'}
    {'2020'}    {'06'}
    {'2020'}    {'09'}
    {'2019'}    {'09'}
    {'2020'}    {'06'}
    {'2019'}    {'09'}
    {'2019'}    {'07'}
    {'2020'}    {'06'}
    {'2019'}    {'08'}
    {'2019'}    {'02'}
    {'2019'}    {'03'}
    {'2019'}    {'08'}
    {'2018'}    {'07'}
    {'2018'}    {'08'}
    {'2018'}    {'09'}
    {'2020'}    {'10'}
    {'2019'}    {'07'}
    {'2018'}    {'09'}
    {'2020'}    {'08'}
    {'2020'}    {'09'}
[~,~,grp] = unique(tkn(:,2),'stable')
grp = 5091×1
     1
     1
     2
     3
     4
     5
     3
     5
     5
     5