how i do weekly average?

Hi all,

I have a matrix of 978*744 which is = no. observation*hours in a month. and the attached mat file is the DateTime vector. I want to make a weekly average.

Thank you in advance.

[Jan]

The MAT file contains the datetime vector of what? I do not have access to a Matlab engine currently, therefore I cannot inspect the MAT file. Otherwise perhaps I could guess, what it contains. But maybe guessing is less efficient than if you explain it.

[Lilya]

thanks Jan for your response. The attached MAT file is the date time of the corresponding measurements (978*744) which also has the same dimension of the hours per month (1*744). Therefore, I want to calculate the weekly average of the measurement from the date time reference matrix (1*744) going throw the index of the two matrices.

I hope this helps to clarify my idea.

thank you

Answer 1

[Andrei Bobrov]

Let data - your array [978 x 744].

For MATLAB >= R2016b (here week -> [Sun : Sat]):

Time = (datetime([2017 7 1 0 0 0]):hours(1):datetime([2017 7 31 23 0 0]))';
% or: Time = datetime(timeCopy);
TT = array2timetable(data','R',Time);
TT_out = retime(TT,'weekly','mean');

For MATLAB < R2016b ( here week -> [Mon : Sun]):

data = data';
Time = (datetime([2017 7 1 0 0 0]):hours(1):datetime([2017 7 31 23 0 0]))';
wd = rem(weekday(Time) + 5, 7) + 1;
ii = [true;diff(wd == 1) == 1];
g = cumsum(ii);
[r,c] = ndgrid(g,1:size(TT,2));
TT_out = [table(Time(ii),'V',{'Time'}),...
                 array2table(accumarray([r(:),c(:)],data(:),[],@mean))];

[Lilya]

:') Thanks so much.

[Tanziha Mahjabin]

Hi,

what about the array with 3 dimensions? I have daily average of SST data (340X285X36) which are (lon,lat,time). I want to have weekly average.

Is the [r,c] line correct? Then how can i mean it? And if possible how can i modify the 'for loop'?So far i have this:

clear all; close all; clc;

path(path,'D:\Radar_job\SST')

ncfile='IMOS_aggregation_20200212T151211Z.nc'; %short time

time2=ncread(ncfile,'time');

time2=ncread(ncfile,'time')./86400+datenum(1981,01,01);

SST_lon=ncread(ncfile,'lon');

SST_lat=ncread(ncfile,'lat');

SST=ncread(ncfile,'sea_surface_temperature');

SST=SST-273.15;

id1=find(SST_lat>-39.9&SST_lat<-36.2);

id2=find(SST_lon>137.1&SST_lon<141.9);

lat1=SST_lat(id1);

lon1=SST_lon(id2);

tvec=datevec(time2);

t=datetime(tvec)

[C,uq,iuq]=unique((tvec(:,1:3)),'rows','stable'); %manually look which rows are full weeks

time3=datenum(C);

wd = rem(weekday(time3) + 5, 7) + 1;

ii = [true;diff(wd == 1) == 1];

g = cumsum(ii);

[r,c] = ndgrid(g,1:size(SST,3));

for i=1:length(time3)

h=figure;

set(gcf,'Position',[200 100 1500 800])

set(gcf,'PaperPositionMode','auto')

m_proj('mercator','lon<gitude>',[137.1 141.9],'lat<itude>',[-39.9 -36.2]);

m_pcolor(lon1,lat1,(SST(id2,id1,i))');

shading interp;

m_proj('mercator','lon<gitude>',[137.1 141.9],'lat<itude>',[-39.9 -36.2]);

m_gshhs_h('patch',[0.7 0.7 0.7],'LineWidth',1.5);

m_grid('ytick',[-90:0.5:90],'xtick',[-180:0.5:180],'tickdir','in','FontSize',14);

colormap jet

colorbar

caxis manual

caxis([15 19])

end