How to separate and order timetable data by year

Question

Joe Wheeler 2021-11-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1587219-how-to-separate-and-order-timetable-data-by-year

编辑： Adam Danz 2021-11-17

data = readtable('USA_SITE_004_final.txt'); %import text file and present as table

data_nan = standardizeMissing(data, -999); %return '-999' values as 'NaN'

hourly_temp_rain_sm = data_nan(:, [1 5 11 26]); %extract key variables

TT = table2timetable(hourly_temp_rain_sm); %form timetable

daily_temp_rain_sm = retime(TT, 'daily', 'mean'); %retime data to obtain daily averages

daily_sm = daily_temp_rain_sm(:,3);

Hi, i have created a timetable and retimed soil moisture data here to obtain daily averages for a period of several years. I now want to be able to obtain a metric for each year and to do this i will need to separate the data into years, keeping the daily averages each year. I hope that makes sense and thank you in advance for any help.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Adam Danz 2021-11-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1587219-how-to-separate-and-order-timetable-data-by-year#answer_832074

编辑：Adam Danz 2021-11-15

在 MATLAB Online 中打开

> I now want to be able to obtain a metric for each year and to do this i will need to separate the data into years, keeping the daily averages each year.

You can use retime with yearly intervals. By storing this in a different variable, you can also keep the daily values.

dt = datetime(1999,1,1) + days(0:1:2000)';
rainfall = rand(numel(dt),1);
TT = timetable(dt, rainfall)  % Daily rainfall
TT = 2001×1 timetable
dtrainfall___________________01-Jan-1999     0.09073
    02-Jan-1999     0.82922
    03-Jan-1999     0.68411
    04-Jan-1999     0.15243
    05-Jan-1999     0.47396
    06-Jan-1999    0.084376
    07-Jan-1999     0.50433
    08-Jan-1999     0.65501
    09-Jan-1999     0.47188
    10-Jan-1999     0.29966
    11-Jan-1999     0.90719
    12-Jan-1999     0.51547
    13-Jan-1999     0.47611
    14-Jan-1999      0.6801
    15-Jan-1999    0.015343
    16-Jan-1999     0.56246
yearlyTT = retime(TT,'yearly','mean')  % yearly avg
yearlyTT = 6×1 timetable
        dt         rainfall
    ___________    ________

    01-Jan-1999    0.52045 
    01-Jan-2000    0.51869 
    01-Jan-2001    0.49597 
    01-Jan-2002    0.50299 
    01-Jan-2003    0.50966 
    01-Jan-2004    0.47196 

Note that the aggregate method can be a function handle if your metric is not a built-in option. See doc retime for more info.

6 个评论
显示 4更早的评论隐藏 4更早的评论

Adam Danz 2021-11-15

编辑：Adam Danz 2021-11-15

在 MATLAB Online 中打开

I would highly recommend to use indexing or to create a simple anonymous function to output a subsection of the timetable by year instead of breaking up timetables. Breaking up the timetable by year would necessitate storing the sub-tables in a cell array which introduces complicated indexing. Surely users should not assign the subtables to different variables since that would either need to be done manually or by using dynamic variable naming which is very poor practice.

For example, if the user wants to temporarily isolate all data from 2001 using an anonymous function,

% Create demo timetable
dt = datetime(1999,1,1) + days(0:1:2000)';
rainfall = rand(numel(dt),1);
TT = timetable(dt, rainfall)  % Daily rainfall
TT = 2001×1 timetable
dtrainfall___________________01-Jan-1999     0.55943
    02-Jan-1999      0.2185
    03-Jan-1999     0.34786
    04-Jan-1999     0.91244
    05-Jan-1999    0.041274
    06-Jan-1999     0.44867
    07-Jan-1999     0.25255
    08-Jan-1999     0.73741
    09-Jan-1999     0.23256
    10-Jan-1999    0.053528
    11-Jan-1999    0.019076
    12-Jan-1999     0.66806
    13-Jan-1999     0.32396
    14-Jan-1999     0.87044
    15-Jan-1999      0.8415
    16-Jan-1999     0.68612
% anonymous fcn: enter year as integer
TTbyYearFcn = @(yr)TT(year(TT.dt)==yr,:); 
% Get values from 2001
TTbyYearFcn(2001)
ans = 365×1 timetable
dtrainfall___________________01-Jan-2001     0.70419
    02-Jan-2001     0.62215
    03-Jan-2001     0.93004
    04-Jan-2001     0.57443
    05-Jan-2001    0.055897
    06-Jan-2001     0.95668
    07-Jan-2001     0.50563
    08-Jan-2001     0.62463
    09-Jan-2001     0.27101
    10-Jan-2001     0.44119
    11-Jan-2001     0.75864
    12-Jan-2001     0.53423
    13-Jan-2001     0.13889
    14-Jan-2001     0.34593
    15-Jan-2001     0.08533
    16-Jan-2001      0.1614
% Example of extracting rainfall from 2001
TTbyYearFcn(2001).rainfall
ans = 365×1
    0.7042
    0.6221
    0.9300
    0.5744
    0.0559
    0.9567
    0.5056
    0.6246
    0.2710
    0.4412

Joe Wheeler 2021-11-16

编辑：Adam Danz 2021-11-17

在 MATLAB Online 中打开

Unfortunately i got this error:

Unable to use a value of type datetime as an index.
Error in Research_Project>@(yr)daily_sm(year(daily_sm.DT)==yr,:) (line 31)
daily_smbyYearFcn = @(yr)daily_sm(year(daily_sm.DT)==yr,:);
Error in Research_Project (line 33)
A = daily_smbyYearFcn(2001);

Adam Danz 2021-11-16

编辑：Adam Danz 2021-11-17

What Matlab release are you using?

I'm assuming daily_sm.DT contains datetime values. Does year(daily_sm.DT) throw an error?

Or maybe you have a variable named "year" which is preventing use of the function of the same name.

请先登录，再进行评论。

How to separate and order timetable data by year

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

回答（1 个）

6 个评论
显示 4更早的评论隐藏 4更早的评论

另请参阅

类别

标签

Community Treasure Hunt

How to separate and order timetable data by year

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

回答（1 个）

6 个评论 显示 4更早的评论隐藏 4更早的评论

另请参阅

类别

标签

Community Treasure Hunt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

6 个评论
显示 4更早的评论隐藏 4更早的评论