How to assign a mean of a variable to every year ?

Hello,

I have Sea surface temperature per year but I have many values for the same year. How to calculate the mean of SST for every year?

Thank you.

This is the table:

Answer 1

[KSSV]

T = readtable(myfile) ;

[c,ia,ib] = unique(T.(1)) ;   % gewt unique values of years 
N = length(c) ; 
iwant = zeros(N,2) ;
for i = 1:N
    iwant(i,1) = c(i) ;
    iwant(i,2) = mean(T.(3)(ib==i)) ;
end

[HADJ MOHAMMED]

Thank you so much

Answer 2

[Stephen23]

The simple and efficient MATLAB approach:

DateYear = [2016;2016;2010;2008;2016;2016;2009;2008;2007;2010];
SeverityCode = [3;3;0;2;3;3;1;1;2;0];
SST = [26.33;26.77;29.05;28.61;26.71;25.37;27.1;27.95;28.62;-11];
T = table(DateYear,SeverityCode,SST)

T = 10×3 table
    DateYear    SeverityCode     SST 
    ________    ____________    _____

      2016           3          26.33
      2016           3          26.77
      2010           0          29.05
      2008           2          28.61
      2016           3          26.71
      2016           3          25.37
      2009           1           27.1
      2008           1          27.95
      2007           2          28.62
      2010           0            -11

G = groupsummary(T,'DateYear','mean','SST')

G = 5×3 table
    DateYear    GroupCount    mean_SST
    ________    __________    ________

      2007          1           28.62 
      2008          2           28.28 
      2009          1            27.1 
      2010          2           9.025 
      2016          4          26.295 

Note that if the value -11 represents invalid data then those lines will need to be modified e.g. removed from the table or -11 replaced with NaN:

T.SST(T.SST==-11) = NaN

T = 10×3 table
    DateYear    SeverityCode     SST 
    ________    ____________    _____

      2016           3          26.33
      2016           3          26.77
      2010           0          29.05
      2008           2          28.61
      2016           3          26.71
      2016           3          25.37
      2009           1           27.1
      2008           1          27.95
      2007           2          28.62
      2010           0            NaN

G = groupsummary(T,'DateYear','mean','SST')

G = 5×3 table
    DateYear    GroupCount    mean_SST
    ________    __________    ________

      2007          1           28.62 
      2008          2           28.28 
      2009          1            27.1 
      2010          2           29.05 
      2016          4          26.295 

[HADJ MOHAMMED]

thank you so much

Answer 3

[Image Analyst]

Like @Stephen23 said, you can use groupsummary. Other options are splitapply and grpstats. Let us know if you can't figure it out.