Calculate monthly averages without reshaping

Question

aaron Harvey 2016-2-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/268804-calculate-monthly-averages-without-reshaping

编辑： Stephen23 2016-2-24

i have a time series of data and i would like to calculate monthly averages but keeping the vector lengths the same. (the variables also contain many nans)

For example if i have a date vector (yyyymm):

How can i get

variable_montlyav=
2
2
2
4.5
4.5
6
nan (or 6 i dont mind)
6

so that i can use my new montly averaged variable with some existing codes i have.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Stephen23 2016-2-22

编辑：Stephen23 2016-2-24

在 MATLAB Online 中打开

What exactly do you mean by a "date vector"? In MATLAB the term "date vector" has a specific meaning, which is a numeric vector consisting |y,m,d,H,M,S.F] values. If your data really was a date vector, it would looks like this:

        1999           1           1           0           0           0
        1999           1           1           0           0           0
        1999           1           1           0           0           0
        1999           5           1           0           0           0
        1999           5           1           0           0           0
        2001           7           1           0           0           0
        2001           7           1           0           0           0
        2001           7           1           0           0           0

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stephen23 2016-2-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/268804-calculate-monthly-averages-without-reshaping#answer_210747

编辑：Stephen23 2016-2-24

在 MATLAB Online 中打开

Note: this code works if date is a cell array of strings, and also if date is a numeric vector of values representing year and month.

date = {'199901','199901','199901','199905','199905','200107','200107','200107'};
variable = [1,2,3,4,5,5,6,7];
[~,~,idx] = unique(date);
tmp = accumarray(idx(:), variable, [], @mean);
tmp(idx)

creates this output:

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

aaron Harvey 2016-2-23

worked perfectly! i dunno how it works but it does :)

请先登录，再进行评论。

Answer 2

Roger Wohlwend 2016-2-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/268804-calculate-monthly-averages-without-reshaping#answer_210745

在 MATLAB Online 中打开

A = accumarray(date, variable, [], @mean);
MeanValues = A(date);

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Stephen23 2016-2-22

This is not a very memory-efficient solution, as it will create temporary arrays with more than 200000 elements in them. See my answer for a more memory-efficient solution.

请先登录，再进行评论。