MATLAB: How to find the yearly average with repeating years

datetime mean

I have 55170×1 datetime matrix and 55170×1 water_level numeric matrix. The datetime is in years, repeating the same year through many consecutive cells before moving on chronologically. I want to find the mean water level for each year.

Best Answer

use grpstats()

meanYearly=grpstats(waterLevel,year);

EDIT: I really recommend using grpstats, but if somehow you don't want to use it, or if you don't have statistics toolbox then alternatively you can compute mean yearly as follow:

meanYearly= arrayfun( @(yy) mean(waterLevel(year==yy)), unique(year));

Related Solutions

MATLAB: Daily 3d array to monthly- dealing with alternate days in a month and leap years – How to do it

You don't have another option than just hardcoding the number of days in a month. You can do this in a fancy way using the date functions in Matlab, or just look at a calender. The fact that you have 365 days means that you are dealing with a non-leap year, so February only has 28 days.

There are probably simpler ways to solve it, but you can easily convert this 3D matrix to a cell array, apply the function you already suggested to each cell and then convert back to a 3D matrix.

A=rand(720,360,365);%generate example array
month_lengths=[31 28 31 30 31 30 31 31 30 31 30 31];%non-leap year
B=mat2cell(A,size(A,1),size(A,2),month_lengths);%divide into 1 cell per month
B=cellfun(@(x) mean(x,3),B,'UniformOutput',false);%find mean for each month
B=cell2mat(B);%convert back to 3D array

MATLAB: Determining the total value of the number in each position of a matrix that corresponds to another same length matrix

>> year = [2007;2009;2011;2018;2007;2007];
>> medals = [1;1;5;7;3;1];
>> [uni,~,idx] = unique(year);
>> cnt = accumarray(idx,medals);
>> [uni,cnt]
ans =
   2007      5
   2009      1
   2011      5
   2018      7

Best Answer

Related Solutions

MATLAB: Daily 3d array to monthly- dealing with alternate days in a month and leap years – How to do it

MATLAB: Determining the total value of the number in each position of a matrix that corresponds to another same length matrix

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