Question

我每天都有＆＃39; .mat＆＃39;文件的命名类似于＆＃39; Data_grid_day_ppt_ice003.mat＆＃39;，最后的＆＃39;＆＃39;是朱利安日格式的年份日期，它可以从＆＃39; 001＆＃39;开始。并以＆＃39; 365＆＃39;结束和＆＃39; 366＆＃39;取决于它是否是闰年。

我需要每月平均数据。知道如何为日期文件创建循环？

某些日期也可能丢失，因此仅计算文件数量将无效。

我在Matlab写作，我正在尝试像

这样的东西

year = linspace(2007,2016,10); % Years of data
months = linspace(01,12,12);% Months of the year
for n = 1:length(year) 
    foldery = int2str(year(n));
    if ~exist(folderyear) 
        continue
    else
        if mod(year,4) == 0 % if the year is divisible by four 
            dpm = [31 60 91 121 152 182 213 244 274 305 335 366];      
        else 
           dpm = [31 59 90 120 151 181 212 243 273 304 334 365];     
        end
        for j = 1:length(months) %loop over months
            if ~exist(months) 
                continue
            else
                for ii = 1:dpm(j)   %loop over days
                    % ... Not sure what to do here ...
                end 
            end
        end
    end
end

但是，我无法完成下一步......

Answer 1

首先，不要使用year作为变量名，因为它是内置的Matlab函数！然后小心使用变量名称，例如混淆foldery和folderyear。

最简单的方法是将一年中的某一天添加到该年的1月1日，然后使用内置month功能的Matlab获取月份。只要您知道这一年（您似乎），这将照顾所有闰年问题。另请参阅此文档Date and Time Arithmetic，该文档确认在日期时间值中添加数字将添加完整的24小时日。

关键是这种方法可以从一年中的Julian日算起一个月：

thisyear = 2017;               % Define which year you're in
J1 = datetime(2016,1,1);       % Set January first datetime 
dayofyear = 360;               % Christmas day as an example!
m = month(J1 + dayofyear - 1)  % Add day of year to Jan 1st, get month
% J1 + dayofyear - 1 = 25-Dec-2016 00:00:00
% m = 12
% month(J1 + dayofyear - 1, 'name') = 'December'

有关更多详细信息，请参阅此代码的注释扩展...

y = 2007:2016; % Years of data [2007, 2008, ... 2016]
outputdata = cell(1,12);
for n = 1:length(y) 
    folderyear = int2str(y(n));
    if ~exist(folderyear, 'dir') 
        continue
    else
        % Get all .mat files within this year folder
        f = dir(fullfile(folderyear, '*.mat'));
        filenames = {f.name};
        % Set Jan 1st date
        J1 = datetime(y, 1, 1);
        % Loop over months
        for m = 1:12
            % Loop over files
            for myfile = 1:numel(filenames)
                % Get number from end of file name
                dayofyear = filenames{myfile};
                dayofyear = str2num(dayofyear(end-6:end-4));
                % Get month of day by adding to Jan 1st of that year
                % -1 used assuming Jan 1st is day 1. Not needed if Jan 1st is day 0.
                if month(J1 + dayofyear - 1) == m  
                    % hurrah, this file is in the month m, add it to an average
                    % or anything else you want, then you could assign to 
                    % an output cell or matrix
                    % outputdata{m} = ...
                end
            end
        end     
    end
end

Answer 2

如果我做Num = regexp(dayofyear,'\d','Match'); tt=cellstr(Num{:}); pp = strcat(tt(1),tt(2),tt(3)); dayofyear=str2double(pp);现在即将到来虽然它有点幼稚，但如果我在一行中这样做会返回错误：P Thanku Wolfie：）

按天数循环每月或每年平均值（以朱利安日格式）

2 个答案: