Calculate weekly mean from temperature data

Hi!

Can anyone help me to calculate weekly means of temperature data (td= SST - bottom temp difference) and salinity data? Time is from 1st of July till 31st of August 2022 (hour 12:00:00 for every day).

Could not attach the data as mat files they are too big. My variables include:

td(temperature difference) =783x1230x62 double

sal=4-D double

time = 62x1 datetime

My friend used this code for the same procedure, but I need to change the number of weeks as it's different from my data (she had 13 weeks). I also don't know how to interpret what she did in the calculations ( (w-1)*7+1:w*7) ) so don't know how to apply it to my data. Thanks in advance!

for w = 1:13
    tdw(:,:,w) = mean(td(:,:,(w-1)*7+1:w*7),3);
    salw(:,:,:,w) = mean(sal(:,:,:,(w-1)*7+1:w*7),4);
end

Answer 1

[Antoni Garcia-Herreros]

Hello Giulia,

You may try something like this.

If you need more info on conditional statements, you can refer to this page

td=rand(783,1230,62); %Generate variables for the example
sal=rand(783,1230,3,62);

l=1:7:size(td,3); % Indices to separate the days in the week e.g. 1 8 15 ...
tdw=zeros([size(td,[1 2]) size(l,2)]); % Array where the means of td for every week will be stored
salw=zeros([size(sal,[1 2 3]) size(l,2)]); %Same but for sal

for i=1:numel(l) %Loop through the first day of the weeks 1 8 15 ...
    
    if i+1>numel(l) % This will only be true for the last week. Because if we call l(i+1) it will give us an error
        % And because the last week is not 7 days, we take the mean of td
        % and sal from day l(end), 57, to end of td, 62
        tdw(:,:,i)=mean(td(:,:,l(i):end),3);
        salw(:,:,:,i) = mean(sal(:,:,:,l(i):end),4);
    else % The rest of the iterations will enter here, where we take the mean between of td or sal between the first and last day of week i 
        tdw(:,:,i)=mean(td(:,:,l(i):l(i+1)-1),3);
        salw(:,:,:,i) = mean(sal(:,:,:,l(i):l(i+1)-1),4);
    end
end

Hope this helps!

[Giulia]

Thanks a lot Antoni!! That works! All the best.

[Giulia]

Hi again Antoni, just as a clarification as I am quite new to Matlab...what is the 'if ... else ... end' statement used for? Thanks!

[Giulia]

Thanks again for the clarification!

Best