Grouping minute data by day and assigning to a variable

Hey guys, I have an electricity load data in the following format

and I would like to group them by each day, so that I would have the data in the following format

I was trying to use a while loop, but I am pretty bad at coding.. Is there anyone that could help me out with this issue?

Thanks in advance.

Answer 1

[DGM]

I never really do much with datetime objects, so I'm sure that there are better ways. This is at least a start. This should group the data by day. Note that this does not guarantee that the minutewise samples line up. In this example, two of the days are partial. How such a case is handled (e.g. padding) is up to you.

t1 = datetime(2020,11,1,8,0,0);
t2 = datetime(2020,11,3,8,0,0);
t = (t1:minutes(60):t2).';

data = (1:numel(t)).';

[ty tm td] = ymd(t);
tymd = [ty tm td];
tymdu = unique(tymd,'rows')

tymdu = 3×3

2020 11 1 2020 11 2 2020 11 3

ndays = size(tymdu,1);
outdata = cell(ndays,1);
for d = 1:ndays
    mask = all(tymdu(d,:) == tymd,2);
    outdata{d} = data(mask).';
end
celldisp(outdata)

 
outdata{1} =
 
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16

 
 
outdata{2} =
 
    17    18    19    20    21    22    23    24    25    26    27    28    29    30    31    32    33    34    35    36    37    38    39    40

 
 
outdata{3} =
 
    41    42    43    44    45    46    47    48    49

 

Using the cell array is necessary since there's no guarantee that the sample vectors are the same size. If padding is performed, then a regular array can be used instead:

t1 = datetime(2020,11,1,8,0,0);
t2 = datetime(2020,11,3,8,0,0);
t = (t1:minutes(60):t2).';

data = (1:numel(t)).';

[ty tm td] = ymd(t);
tymd = [ty tm td];
tymdu = unique(tymd,'rows'); % unique days

[th tmn ts] = hms(t);
thms = [th tmn ts];
thmsu = unique(thms,'rows'); % unique sample times

ndays = size(tymdu,1);
nsampperday = size(thmsu,1);
outdata = NaN(ndays,nsampperday);
for d = 1:ndays
    daymask = all(tymdu(d,:) == tymd,2);
    samplemask = ismember(thmsu,thms(daymask,:),'rows');
    outdata(d,samplemask) = data(daymask);
end
outdata

outdata = 3×24

NaN NaN NaN NaN NaN NaN NaN NaN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN

daylabels = datestr([tymdu zeros(size(tymdu))],'yyyy-mm-dd')

daylabels = 3×10 char array
    '2020-11-01'
    '2020-11-02'
    '2020-11-03'

sampletimelabels = datestr([[2000 1 1].*ones(size(thmsu)) thmsu],'HH:MM:SS')

sampletimelabels = 24×8 char array
    '00:00:00'
    '01:00:00'
    '02:00:00'
    '03:00:00'
    '04:00:00'
    '05:00:00'
    '06:00:00'
    '07:00:00'
    '08:00:00'
    '09:00:00'
    '10:00:00'
    '11:00:00'
    '12:00:00'
    '13:00:00'
    '14:00:00'
    '15:00:00'
    '16:00:00'
    '17:00:00'
    '18:00:00'
    '19:00:00'
    '20:00:00'
    '21:00:00'
    '22:00:00'
    '23:00:00'