How can I Repeat time data for a number of days

Hi Guys, I have generated a column vector of one minutes interval time (So I have 1440 rows of time). Now I need repeat the times for 2490 days as I have 2490 trading days in my data set. So my output will be a column that contains 1440 time (from 12.00 AM to 11.59 PM) 2490 times. So total length of the column will be 1440*2490=3585600. Anyone can help plz?

Answer 1

[Star Strider]

Use repmat:

T = [1:1440]';                      % Column Vector Of Minutes
Days = 2490;                        % Days To Replicate
Tv = repmat(T, Days, 1);            % Time Vector (3585600x1)

[Jan]

A small change: 1:1440 is a vector already, so casting it to a vector by additional brackets is not useful. But for the transpose operation, round parenthesis are required.

[Star Strider]

@Jan — By my own convention, I put vectors in brackets so that I know immediately by looking at them that they are vectors. It is redundant perhaps, but not wrong. The transpose operation works with square brackets.

[Jan]

Yes, this is not wrong. It consumes just a really tiny overhead, but it is measurable. But if this helps to improve the readability of the code, the time saved for debugging will be more important.

[Mohammad Sayeed]

Thank you @Star for the codes. It worked perfectly with the vector you have generated as T = [1:1440]. I have generated the time vector as follows: dv=0/24:1/1440:23/24+59/1440; DV=datestr(dv)

Thus DV is giving me times from 12.00 AM to 11.59 PM. Now I want to repeat it 2490 times but it is not working by using repmat. May be because the data type is not numeric. Do you know anyway how can I work with time type of data as numeric data? Such as I need to generate a matrix where My first column will be date, second column time and third to other columns with stock prices. I have such data table in csv files. But I could not import it in MATLAB as it is. Can you give me any suggestion or anything to read? Thank you. Thanks @Jan also.

[Star Strider]

My pleasure.

If you want a continuous vector of dates and times starting at a specific date and time and then going every minute for 2490 days, this works:

start = now;                        % Choose Starting Date As ‘datenum’
DNV = start + [0 : 1/1440 : 2490];  % Create Vector Of Minutes For 2490 Days
DV = datevec(DNV);                  % Convert To ‘datevec’ Strings

Q = [DS(1:3,:); DS(end-2:end,:)];   % See Sample Output For Series

This creates a vector of date numbers in ‘DNV’, converts them to date vectors in ‘DV’ (since you want numeric data for your stock price array).

You can convert them to date strings using datestr rather than datevec, but it takes forever with a vector that size. If you do that, save that vector in a .mat file so you don’t have to recalculate it.

My ‘Q’ assignment has the first three and last three minutes of the entire series to demonstrate that the code works. It is for demonstration purposes only and is not a part of the code.

[Mohammad Sayeed]

Thank you @Star. It is indeed very helpful. Thank you again.

[Star Strider]

Again, my pleasure.