Wrong date while importing .csv

Having a problem when i import daily .csv files. More specifically, when i plot my xy data(x axis contains date and time stamp), in every different daily file, MATLAB shows todays date. Any ideas?

[madhan ravi]

Upload your file by clicking the paper clip button.

[madhan ravi]

can you upload your code?

[madhan ravi]

Just lookup xticklabels.

[Stephen23]

@Sirius8: this is what one line of the file looks like:

00:00:0;0.0;0.00540500736377

Where is the date? Please show us which parts of that line contain date data.

Answer 1

[jonas]

The date is not automatically assigned because it's not in the data but in the name of the file. You could do something like this:

files=dir('folderpath~\*.csv');
for i=1:length({files.name})
    date=files(i).name;
    date=regexprep(date,'.csv','')
    data=readtable(files(i).name);
    t{i}=data{:,1}+datetime(date);
    xy{i}=data{:,2:3}
end

Now you have two cell arrays, t and xy, where the former has all time data and the latter all other data.

[jonas]

It seems your local settings are different from mine, so readtable interprets the first column as datetime instead of duration. Add these two lines at the beginning of the loop.

    opts=detectImportOptions(files(i).name)
    opts=setvartype(opts,'Var1','duration')

[jonas]

I'm having trouble reproducing the issue. At what line does it say that?

type this and paste the output in comment here:

varfun(@class,data,'OutputFormat','cell')

[jonas]

Alright, what release are you running? We may have to convert the cell to duration subsequent to loading the table. Copy a few rows from the first column here so I can figure out how to convert it. In the meantime, you can try:

TT=timetable(data)

as timetable is sometimes smart enough to figure out the format of the input.

[jonas]

Let's skip readtable altogether and try another import option:

files=dir('folderpath~\*.csv');

for i=1:length({files.name})
    date=files(i).name;
    date=regexprep(date,'.csv','')
    din=importdata(files(i).name,';')
    t{i}=duration(din.textdata,'format','hh:mm:ss')+datetime(date);
    xy{i}=din.data
end

I wouldn't recommend your other solution. Albeit it could work, it is the opposite of robust.

[jonas]

Seems to have been more updates to DURATION than I was aware of but alright, give me a few minutes to fix

[Walter Roberson]

In this situation, let it be imported as datetime, but then do

t{i} = data.Var1 - dateshift(data.Var1, 'start', 'day') + datetime(day);

[jonas]

Thanks Walter, that should do the trick.

If it, for some reason, still does not work. Then this solution should. It's however much slower due to the cellfun

files=dir('folderpath~\*.csv');

for i=1:length({files.name})
    date=files(i).name;
    date=regexprep(date,'.csv','')
    din=importdata(files(i).name,';')
    tday=cellfun(@(x) str2double(strsplit(x,':')),din.textdata,'uniformoutput',false)
    tday=cell2mat(tday);
    t{i}=hours(tday(:,1))+minutes(tday(:,2))+seconds(tday(:,3))+datetime(date);
    xy{i}=din.data
end

The absolute best solution would be to update MATLAB :)

[jonas]

You're welcome! Note that you can just remove the curly braces from the t{i} if you want to achieve that. I put the results in a cell array as I figured you have several data sets that you want to load and store.

Also, don't use datetime as a variable name!!