Average of irregular range of data

I have a time series of satellite data over a bout 6 years. With each pass of the satellite a number of measurements are taken. The number of measurements taken is non-uniform, so anywhere between 2 and 7 for a given pass of the satellite. This occurs every 10 days but there are occasions when the satellite misses a pass. I want to get the average of each pass without having to go through the data and inputting the correct ranges manually. Is there a way of setting a rule so that when the time between two measurements is greater than say a day a new range of data is selected? Any help would be appreciated.

[Andrei Bobrov]

short example of your data, please

[David]

Hi Andrei, here are the first few passes of the satellite, with the figure on the right being the wave height:

09/01/2003 21:05 1.73

09/01/2003 21:05 2.196

09/01/2003 21:05 1.979

19/01/2003 19:03 6.507

19/01/2003 19:03 6.676

29/01/2003 17:02 6.132

29/01/2003 17:02 6.379

29/01/2003 17:02 5.714

08/02/2003 15:00 5.019

08/02/2003 15:00 4.671

08/02/2003 15:00 4.814

08/02/2003 15:00 4.783

08/02/2003 15:00 4.334

Answer 1

[Azzi Abdelmalek]

   data={'09/01/2003 21:05  1.73'
'09/01/2003 21:05  2.196'
'09/01/2003 21:05  1.979'
'19/01/2003 19:03  6.507'
'19/01/2003 19:03  6.676'
'29/01/2003 17:02  6.132'
'29/01/2003 17:02  6.379'
'29/01/2003 17:02  5.714'
'08/02/2003 15:00  5.019'
'08/02/2003 15:00  4.671'
'08/02/2003 15:00  4.814'
'08/02/2003 15:00  4.783'
'08/02/2003 15:00  4.334'}

dates= datenum(data,'dd/mm/yyyy');
weights=cellfun(@(x) str2double(x{3}),regexp(data,'\s+','split'));
[a,b,c]=unique(dates);
average_values=accumarray(c,weights,[],@mean);
out=[cellstr(datestr(dates(b))) num2cell(average_values)]

%or

dates=datenum(data,'dd/mm/yyyy');
s=regexp(data,'\s+','split');
s=[s{:}];
weights=str2double(s(3:3:end))';
[a,b,c]=unique(dates);
average_values=accumarray(c,weights,[],@mean);
out=[cellstr(datestr(dates(b))) num2cell(average_values)];

Answer 2

[Andrei Bobrov]

tresh = 2; % Let greate than two days

f = fopen('PathAndNameYourdata.txt');%'E:\wtdy2.txt'
c = textscan(f,'%s %s %f','CollectOutput',true);
fclose(f);
k = strcat(c{1}(:,1),{' '},c{1}(:,2));
n = datenum(k,'dd/mm/yyyy HH:MM');
ii = [true;diff(n)>tresh];
i1 = cumsum(ii);
i2 = find(ii);
out = [{'start','finish','mean of value'};
  [k([i2,[i2(2:end)-1;numel(n)]]), accumarray(i1,c{2},[],@(x){mean(x)})]];

[David]

Thanks for reply Andrei. I ran this code but the following error message was returned:

Error: File: Mean_swh.m Line: 13 Column: 11 The construct "i3(...end...)" is ambiguous in this context, because "i3" cannot be ascertained to be either the name of a variable or of a function. To make it a variable, assign to it; to allow it to become a function at execution time, replace "end" with a call to LENGTH, SIZE, or NUMEL on the desired array.

[David]

Just changed it around a little and it works perfectly. Thanks for the help Andrei, much appreciated.

[Andrei Bobrov]

Oh! My typo! Corrected.