Calculate the rate of change from 5 minutes interval

Good day, everyone.

As attached is my observations data for 24 hours from different transmitter (PRN) . The data here are from 1/1/2014 to 31/1/2014. From the excel (refer attachment), I already extracted 1-minute average for all PRN in 31 days via the code below.

My problem now is how to calculate the rate of change per 5 minute from data in PRNTT1min. Already done on step 6 on managing time series for 5-mins resampling but I couldn't figure out to find the rate of change. May be the answer is already there but I am completely lost now.

Thank you in advanced.

%_______________1- Read data_______________%
data = readtable("Book_Jan.xlsx");

%___2- Convert DAY and TIME into durations___%
data.DAY = days(data.DAY);
data.TIME = days(data.TIME);

%___3- Create a datetime___%
data.TimeStamp = datetime(2014,01,01) + data.DAY-1 + data.TIME;
data.TimeStamp.Format = "MM-dd-yy HH:mm";

%___4- Convert the table to a timetable___%
dataTT = table2timetable(data,"RowTimes","TimeStamp");

%___5- Use retime to average the PRN data into 1 minute increments___%
PRNTT1min = retime(dataTT(:,["VTEC" "S4" "Sigma"]),"minutely","mean");

%___6- Round time to nearest 5 min and take unique values only___%
tt = data.TimeStamp;
tt.Minute = 5 * floor(tt.Minute/5); %5 means for 5 mins resampling
tt.Second = 0;
NEWTIMESTEP = unique(tt);
%%%%%___PROBLEM HERE___%%%%%

%___7- Find rate of change of VTEC, S4, Sigma for 5 mins___%
%%%%%___NEED HELP HERE TOO___%%%%%

Answer 1

[Mathieu NOE]

hello Ann

welcome back !

here the end of the code , I don't know if the rate is per second or per minute, you to decide

%___Use retime to average the data into 5 minute increments___%
dataTT5min = retime(dataTT(:,["VTEC" "S4" "Sigma"]),"regular","mean","TimeStep",minutes(5));

%___7- Find rate of change of VTEC, S4, Sigma for 5 mins___%
all_data = table2array(dataTT5min);
rate_per_seconds = diff(all_data)/(5*60);
rate_per_minute = diff(all_data)/5;

[Ann]

Hi, Mathieu. I owe you!

The code is working but I doubt on something and may be you could help me clear it.

1. Originally, my data data were divided into a variable called PRN which have 31 of them.

2. To make it visibily clear I sort via day and time (per minute) by averaging the data from PRN 1 to PRN 31. That is why it coded as below:

dataTT1min = retime(dataTT(:,["VTEC" "S4" "Sigma"]),"minutely","mean");

3. Next, I am to try find the rate of change per 5 minutes (thanks for your help) therefore I am using dataTT1min instead of dataT5min. Am I doing it right? Because if I am using dataTT5min (like your code) it might resulting clash of interest in number 2.

I think I might go bald after keep questioning myself.

[Mathieu NOE]

hmm

do you mean , you would prefer to make the diff on the 1 min data and then eventually look only every 5 mins ? that might just give the same results ...

[Ann]

Mathieu, I cleared now! Though the raw data is being averaged by PRN for 1 minute or 5 minute, both will give the same result for their rate of change of 5 minute.

[Mathieu NOE]

good !!

[Ann]

Thank you, Mathieu. You did help me a lot.

[Mathieu NOE]

Glad I could be of some help !!

good luck for the future !

Answer 2

[Jason]

how to prove in matlab: fA spherical iron ball 8 inches diameter is coated with a layer of ice of uniform thickness. If the ice melts at a rate of 14 inches3/minute, how fast is the thickness of the ice decreasing when it is 2 in.​ thick?

[Mathieu NOE]

please make a separate post if you have a new question