Wrong Date format with Readtable for CSV

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Logesh Velusamy 2019-11-29

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评论： dpb 2019-11-29

Hello,

I am trying to import multiple csv files into matlab with Date/Time and other data to plot. READTABLE (including date/time format specified) works fine for data files which have dates greater than 13 but not for anything below 13 as it converts to different format irrespective of me defining the format upfront.

Can anybody help me to solve this issue.

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Logesh Velusamy 2019-11-29

在 MATLAB Online 中打开

Apologies for not posting the code in first place.

I am running following code to read files from a directory and looping through to store imported data in structure.

Once this is done, I am going through another loop to convert structure to array and apply date format and plot data with the below code.

I have attached two sample *.csv files for reference.

Thanks.

% 
files = dir('C:\Test\*.csv');
fullpaths = fullfile({files.folder}, {files.name});
for i=1:length(files)
    Data(i).name = readtable(files(i).name);   
end
% 
for i = 1:length(files)
      
    New_Data = struct2array(Data(i));
    M = datetime(New_Data.Date,'InputFormat','dd-MM-yyyy');
    t = datetime(New_Data.Time,'InputFormat','HH:mm:ss.SSS');
    t.Format= 'HH:mm:ss.SSS';
    New_Data.Datetime = M + timeofday(t);
    New_Data.Datetime.Format = 'MM.dd.uuuu HH:mm:ss.SSS';
        
    if New_Data(i).Fuel_SP > 420 & New_Data(i).Fuel_SP <560
        
        figure(1)
        subplot(2,1), scatter(New_Data(i).Datetime,New_Data(i).FuelPump_rpm);
        xlabel('Date');
        ylabel('Fuel Pump Speed, rpm');
        title('Fuel Pump Speed vs Date');
        grid('on');
        grid('minor');
        hold on  
        
        subplot(2,2), scatter(New_Data(i).Datetime,New_Data(i).FuelPump_Volts);
        xlabel('Date');
        ylabel('Fuel Pump Volts, V');
        title('Fuel Pump Volts vs Date');
        grid('on');
        grid('minor');
        hold on 
    
    else
    end     
end

Stephen23 2019-11-29

编辑：Stephen23 2019-11-29

"When I am looking at the data in CSV, I am seeing something like this"

Because you are using Microsoft Excel to view the file, which performs lots of magic on the file data before it is displayed. Just to make that clear: Excel does NOT display CSV (or even XLS/X data, for that matter) exactly as it is saved in the file: it performs many conversions based on the locale settings and the number settings and the date settings and no doubt other magic... in short, do NOT rely on Excel if you really want to know what is saved in a file.

I strongly recommend that you view text files (which is what CSV files are) using a text editor.

"I am not sure why it is showing like that in text editor."

Becaue that is what your CSV file actually contains. There is no way to avoid the fact that your CVS file is missing the hour data.

"Will that impact the date formatting even though I am not using time column?"

It should not affect the date, but it will affect the time of day.

dpb is correct: you should fix the file writing, not try to fix this data-bug in MATLAB.

Logesh Velusamy 2019-11-29

Stephen Cobeldick, dpb

Thanks for your help guys, I will try fixing this in the export software.

dpb 2019-11-29

Will that impact the date formatting even though I am not using time column?

You can, of course, simply ignore the time column, but if you do all the data for the given day will be plotted on top of itself as a blob of points. If that's the intent, ok; if not, "not so much".

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