Extract the most recent values from appended .CSV in MATLAB - matlab

Question

I have a .csv file which is appended with 3 new values in the row below the previous set:
dlmwrite('MyFile.csv', [MyValue,MyValue2,MyValue3], '-append');
This happens every minute. It happens indefinitely because of a timer i.e it accumulates data over time:
How can I continually copy over the 60 most recent sets of values from the file and store them in a new csv file, say MyFile2.The row number of the .csv file is increasing by 1 with every minute. i.e 60 values stored in 60 minutes but I may have 100 values and want to extract the latest 60 for another file.
Image of the CSV file - 2nd column is time in HOURS:MINUTES without the : separator (ignore the lapse in time between rows 38 and 39 or any lapses elsewhere):
Note: MyValue is added to the file every minute because the script is run every 60 seconds from another script. I.e there is no internal timer in the main script:
Period = 60; % Update period in seconds
tim = timer('Period', Period, 'ExecutionMode', 'fixedRate',...
'TimerFcn', 'TESTINGFINAL');
start(tim)
stop(tim)
runtmp = fullfile('MyScriptLocation','MyScript');
run(runtmp);

Answer 1

If you want to do this continuously while running I'd suggest some sort of circular buffer arrangement so you always have the last 60 values in memory. This will be easier than trying to work out the current length of your continuously logging file. Basic idea (minus the actual timing code):
% initialising buffer
MyValue1 = zeros(60,1);
while true % for certain values of true
% these go once a minute
mv1 = myfunc1(inputs);
MyValue1 = [MyValue1(2:end); mv1];
dlmwrite('MyFile.csv', [mv1], '-append');
% this goes less frequently, I presume
filename = [datestr(now,30),'.csv']; % dynamic filename
dlmwrite(filename, MyValue1);
end
This way you have both your continuously logging file (updated every minute), and a series of smaller files containing what were the last 60 values at the time they were written (updated hourly, or on some other trigger, as required).
With your timer, one way of doing this would appear to be to keep a simple counter of how many times the acquisition script has run and then use the mod function to check for when this hits a multiple of 60.

Answer 2

This is not a full answer, but I do have an idea if I understand you correctly. This means you probably want to run Matlab 24/7? Or at least non-stop for a certain amount of time? If so, you could try out the command clock, it shows and stores the system time. In your case
time=clock;
where
time(4) holds the hour. So as soon as this parameter changes, you should open your .csv file and save the last 60 values.
However, doing it this way I think is highly energy-consuming. And sadly Matlab does not have a sleep command like for example Unix does, so maybe it would be interesting to look into running this program in another programming language?
Please provide me with comments and feedback since I see that this is not a complete answer (yet)!