Loop through a timeseries and calculate values over a 20min interval

I have a timeseries with data every second for a few months and a function.

I'd like to use a subset of the timeseries as input in a function (every 20min - 1200 timesteps).

So [1:1200 1201:2400 2401:3600 ...] as input d.

How can I loop through the timeseries and get the value every 20min in an array [Time Pressure] and show the resulting value with a timstamp of 20min?

My initial idea was to use a for loop:

nt = ncread('pressure.nc', 'datetime');
Times = datetime(nt, 'convertFrom', 'posixtime', 'Format', 'yyyy-MM-dd HH:mm:ss');
pressure = ncread('pressure.nc', 'pressure');
T = timetable(Times, pressure);

d = T.pressure;
dt = 1 %timestep (1 second)
meth = 1

for i = 1:1200:length(d) %1200 timestepds = 20 min
    [X] = myfunction(d, dt, meth)
end

Answer 1

[Siegmund Nuyts]

I found a solution using a different approach:

nt = ncread('pressure.nc', 'datetime');
Times = datetime(nt, 'convertFrom', 'posixtime', 'Format', 'yyyy-MM-dd HH:mm:ss');
pressure = ncread('pressure.nc', 'pressure');

T = timetable(Times, pressure);
dt = 1 %timestep (1 second)
meth = 1

interval = 1200;
timespan = length(T.pressure)-interval;

for jj = 1:interval:timespan
    d = T.pressure(jj+(0:interval-1));
    s = T.Times(jj);
    
    [X] = myfunction(d, dt, meth)
    
    XT = [XT; X]
    Time = [Time; s]
end

TT = timetable(Time, XT);