How to extrapolate data with NaN data series?

Question

Tyann Hardyn 2021-10-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1575203-how-to-extrapolate-data-with-nan-data-series

回答： Chunru 2021-10-30

Hi, everyone

I want to ask about how to extrapolate a data series with NaN in the data. So i have a data series like this :

magnetH = [21340; 21340; 21340; 21341; 21341; NaN; NaN; 21340; NaN; NaN]
time_series = [1978-03-29 00:00:00; 1978-03-29 00:01:00; 1978-03-29 00:02:00; 1978-03-29 00:03:00
               1978-03-29 00:04:00; 1978-03-29 00:05:00; 1978-03-29 00:06:00; 1978-03-29 00:07:00
               1978-03-29 00:08:00; 1978-03-29 00:09:00]
extrapolat_time = [1978-03-29 00:00:00; 1978-03-29 00:01:00; 1978-03-29 00:02:00; 1978-03-29 00:03:00
               1978-03-29 00:04:00; 1978-03-29 00:05:00; 1978-03-29 00:06:00; 1978-03-29 00:07:00
               1978-03-29 00:08:00; 1978-03-29 00:09:00; 1978-03-29 00:10:00; 1978-03-29 00:11:00
               1978-03-29 00:12:00; 1978-03-29 00:13:00; 1978-03-29 00:14:00; 1978-03-29 00:15:00
               1978-03-29 00:16:00; 1978-03-29 00:17:00; 1978-03-29 00:18:00; 1978-03-29 00:19:00]

The time series data is a combination between datetime and duration data (yyyy-MM-dd hh:mm:ss) with 1 minute of space between each data. Now, i want to extrapolate the data of magnetH to be defined at extrapolat_time data series....

Would it be possible anyone? Thanks for your help and cooperation.... Iam very grateful, if someone can solve my problem...

/.\ /.\ /.\

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Answer 1

Chunru 2021-10-30

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https://ww2.mathworks.cn/matlabcentral/answers/1575203-how-to-extrapolate-data-with-nan-data-series#answer_820203

magnetH = [21340; 21340; 21340; 21341; 21341; NaN; NaN; 21340; NaN; NaN];
% The original time_series statement are invalid
time_series = ["1978-03-29 00:00:00"; "1978-03-29 00:01:00"; "1978-03-29 00:02:00"; "1978-03-29 00:03:00"; ...
               "1978-03-29 00:04:00"; "1978-03-29 00:05:00"; "1978-03-29 00:06:00"; "1978-03-29 00:07:00"; ...
               "1978-03-29 00:08:00"; "1978-03-29 00:09:00"];
t = datetime(time_series, "Format", "yyyy-MM-dd HH:mm:ss")
t = 10×1 datetime array
   1978-03-29 00:00:00
   1978-03-29 00:01:00
   1978-03-29 00:02:00
   1978-03-29 00:03:00
   1978-03-29 00:04:00
   1978-03-29 00:05:00
   1978-03-29 00:06:00
   1978-03-29 00:07:00
   1978-03-29 00:08:00
   1978-03-29 00:09:00
% extrapolat_time = [1978-03-29 00:00:00; 1978-03-29 00:01:00; 1978-03-29 00:02:00; 1978-03-29 00:03:00
%                1978-03-29 00:04:00; 1978-03-29 00:05:00; 1978-03-29 00:06:00; 1978-03-29 00:07:00
%                1978-03-29 00:08:00; 1978-03-29 00:09:00; 1978-03-29 00:10:00; 1978-03-29 00:11:00
%                1978-03-29 00:12:00; 1978-03-29 00:13:00; 1978-03-29 00:14:00; 1978-03-29 00:15:00
%                1978-03-29 00:16:00; 1978-03-29 00:17:00; 1978-03-29 00:18:00; 1978-03-29 00:19:00]
ti = t(1) + (0:19)'/(24);
% using fillmissing to replace the nans.
magnetHi = interp1(t, fillmissing(magnetH, 'linear'), ti, 'linear', 'extrap')
magnetHi = 20×1
	1.0e+04 *

    2.1340
    2.1322
    2.1302
    2.1282
    2.1262
    2.1242
    2.1222
    2.1202
    2.1182
    2.1162