Reading a large csv and converting to timetable

I have a large .csv (7179x72001) where the first column is filled with datenums and the remaining columns are numerical values. The only way I have been successful in reading this data is by using csvread() and it usually takes about 20 minutes.

I have a second .csv which contains the same values but in datetime format and I would like to compare the two.

Is it possible to convert the first column in the large file so that the values are datetimes, and then in turn convert this to a timetable?

I can do this but I only want to convert the first column, not the whole dataframe:

newtable=datetime(dataframe, 'ConvertFrom', 'datenum');

[KSSV]

Did you try readtable?

[Louise Wilson]

Yeah, I have tried with readtable() but the problem is that in this format I get a message when I try to preview and it takes ~10 min to preview using head(table)

Cannot display summaries of variables with more than 524288 elements.

[Louise Wilson]

I have just tried this:

thetable=readtable(fullfile(foldername,'001Noises_5103_PSD_1sHammingWindow_50%Overlap_output.csv'));

datetime(thetable.Var1,'ConvertFrom','datenum');
head(thetable)

This doesn't give any errors but the contents of the first column remain as datenums.

[Louise Wilson]

Ah, I see now that it should be this:

tt.Var1=datetime(tt.Var1, 'ConvertFrom','datenum');

This works! Thanks for your help!!

Answer 1

[Louise Wilson]

tt.Var1=datetime(tt.Var1, 'ConvertFrom','datenum');

[darova]

You can accept your own answer so it could help someone else

[Louise Wilson]

Thanks!