How do I find the maximum value of every 7 days

Hello!

I have a matrix consisting of daily maxima water levels. For a project, i need to find the weekly maxima. To do so, I want to find the maximum values of every 7 rows. For example:

[year month day Waterlevel]

2000 1 1 94

2000 1 2 95

2000 1 3 98

2000 1 4 101

2000 1 5 103

2000 1 6 104

2000 1 7 105

2000 1 8 106

2000 1 9 106

2000 1 10 104

2000 1 11 102

2000 1 12 102

2000 1 13 101

2000 1 14 99

These are the first 14 rows of my matrix. So i want to find the maximum value of rows 1:7 and then 8:14, 15:21 and so on. Also, I wish to keep the days

Answer 1

[KSSV]

d = (1:36)' ;   % let this be number of days 
z = rand(size(d)) ;  % let this be your water level 

% make d divisble by 7 for reshaping 
n = length(d) + (7 - rem(length(d),7)) ; 
n = n-length(d) ; 

d = [d ; NaN(n,1)]  ;   % append NaN's if extra values are needed 
z = [z ; NaN(n,1)] ;    % append NaN's if extra values are needed 
% reshape to 7 rows 
d = reshape(d,7,[]) ; 
z = reshape(z,7,[]) ; 
iwant = max(z) ;  % get maximum for each 7 days 

[Michiel Smit]

Thanks very much!!