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How to convert string to datetime format in parquet file format within parquet datastore?

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Maitreyee Dey
Maitreyee Dey 2020-7-14
编辑： Stephen23 2020-7-15
The below is the sample parquet datastructure that i am using.
This is the structure of the data. Where both the date and time are in string format. This is the data that have been converted in csv to parquet. I have tried many times to convert second and third column into datetime format. So that I can write some query to operate/plot on perticular duration for analysis.
So the question is how to convert the string into second and third column into datetime format in parquet file format?
I am using Matlab 2020a.
Many Thanks in advance!

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Stephen23
Stephen23 2020-7-15
编辑：Stephen23 2020-7-15
>> D = {'2020/1/1' ;'2020/1/1' ;'2020/1/1' };
>> T = {'00:01:0:0';'00:01:0:60';'00:01:0:320'};
Method one: sscanf and duration:
>> M = sscanf(sprintf(' %s:',T{:}),'%f:',[4,Inf]).';
>> dt = datetime(D,'InputFormat','yyyy/M/d') + duration(M(:,1),M(:,2),M(:,3),M(:,4))
dt =
01-Jan-2020 00:01:00
01-Jan-2020 00:01:00
01-Jan-2020 00:01:00
>> dt.Second % check the milliseconds:
ans =
0
0.0600
0.3200
Method two: regexprep:
>> C = strcat(D,'@',regexprep(T,{':(\d)$',':(\d\d)$'},{':00$1',':0$1'}));
>> dt = datetime(C,'InputFormat','yyyy/M/d@H:m:s:SSS')
dt =
01-Jan-2020 00:01:00
01-Jan-2020 00:01:00
01-Jan-2020 00:01:00
>> dt.Second % check the milliseconds:
ans =
0
0.0600
0.3200
  2 个评论
Maitreyee Dey
Maitreyee Dey 2020-7-15
Thank you for the answer.
Sorry i might not explain properly what I need,
I have 1440 files for a day and each file consists of 6000 rows indicating each 10ms intervals of data.
I have successfully converted them into csv to parquet but can't able convert the two strings colum into datetime format. I have attached one file in csv format from the datalake as I won't be able to attached the parquet file. PFA. If this one
As you mentioned the below how can i automatically setect these values instead?
D = {'2020/1/1' ;'2020/1/1' ;'2020/1/1' };
T = {'00:01:0:0';'00:01:0:60';'00:01:0:320'};
i.e., if the file name
data = readtable('P3007768_2020-01-01-00-59-00.csv');
D = data(:,2);
T = data(:,3);
and then what will be the code of method one and two? how I can convert them into datetime format into another column or may merge these two columns into one and save a new file?
Where the column looks like
01-Jan-2020 00:59:00:00
......
01-Jan-2020 00:59:59:990

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