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Write missing data as NaN

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Danilo M
Danilo M 2018 年 7 月 16 日
コメント済み: dpb 2018 年 7 月 16 日
I have multiple rain time series with 15 minute interval, but with some missing datas, like this:
yyyy mm dd hh mm ss data
2000 01 30 11 00 00 3.00
2000 01 30 11 15 00 2.00
2000 01 30 11 45 00 0.00
2000 01 30 12 00 00 0.00
And I need to add the missing datas with NaN at data row, resulting this
yyyy mm dd hh mm ss data
2000 01 30 11 00 00 3.00
2000 01 30 11 15 00 2.00
2000 01 30 11 30 00 NaN
2000 01 30 11 45 00 0.00
2000 01 30 12 00 00 0.00
There's some way to do that in MatLab?
Tks
  4 件のコメント
Adam Danz
Adam Danz 2018 年 7 月 16 日
Got it. Q3) What's the last element of each row ('data')?
Danilo M
Danilo M 2018 年 7 月 16 日
There's nothing specific at the end of the matrix. It's just the last instant measured by the gauge, like
2017 12 31 23 45 00 00.00

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採用された回答

dpb
dpb 2018 年 7 月 16 日
編集済み: dpb 2018 年 7 月 16 日
OK, without timetable and retime...
dt=(datetime(data(1,1:6)):minutes(15):datetime(data(end,1:6))).'; % build the full time vector
t=table(dt,nan(size(dt)),'VariableNames',{'Time','Rain'}); % empty table
ix=ismember(t.Time,datetime(data(:,1:6))); % data available locations
t.Rain(ix)=data(:,end) % and insert...
t =
5×2 table
Time Rain
____________________ ____
30-Jan-2000 11:00:00 3
30-Jan-2000 11:15:00 2
30-Jan-2000 11:30:00 NaN
30-Jan-2000 11:45:00 0
30-Jan-2000 12:00:00 0
>>
  2 件のコメント
Danilo M
Danilo M 2018 年 7 月 16 日
Tks a lot, dpb, it worked perfectly!
dpb
dpb 2018 年 7 月 16 日
U're welcome, as always, "more than one way to skin..." :)
Note one could do the same thing with the array by converting back via datevec if need be but the table is really a useful data structure as long as doesn't get too large that performance begins to lag.

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その他の回答 (2 件)

dpb
dpb 2018 年 7 月 16 日
tt=timetable(datetime(data(:,1:6)),data(:,end));
tt.Properties.VariableNames={'Data'};
tt=retime(tt,tt.Time(1):minutes(15):tt.Time(end))
tt =
5×1 timetable
Time Data
____________________ ____
30-Jan-2000 11:00:00 3
30-Jan-2000 11:15:00 2
30-Jan-2000 11:30:00 NaN
30-Jan-2000 11:45:00 0
30-Jan-2000 12:00:00 0
  2 件のコメント
Danilo M
Danilo M 2018 年 7 月 16 日
Tks a lot, but I guess my matlab version does not have timetable function. I'm using R2015a and returns "Undefined function or variable 'timetable'"
dpb
dpb 2018 年 7 月 16 日
Bummer! About first time found it to be useful adjunct... :) Unfortunately, retime came along with it also in R2016b. Can't update, I suppose?
Something similar to the other solution is the way although probably some shorter paths to the same end are possible.

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Adam Danz
Adam Danz 2018 年 7 月 16 日
編集済み: Adam Danz 2018 年 7 月 16 日
Here's another method that keeps the data in matrix format but dpb's answer is quicker and more direct.
This method creates a list of all possible time stamps between two bounds given a sample rate. Then it assigns NaN data to each time stamp, finds the time stamps you've got, and fills in the data you got.
startDate = '01/30/2000 11:00:00';
endDate = '01/1/2001 12:00:00';
sampleRate = '00:15:00'; %every 15 min
% Create all possible time stamps
allTimeStamps = datetime(startDate, 'Format', 'MM/dd/yyyy HH:mm:ss') : ...
minutes(15) : datetime(endDate, 'Format', 'MM/dd/yyyy HH:mm:ss');
% Convert to matrix of time-vectors
allTimeStamps = datevec(allTimeStamps');
% Create your (fake) rain data and time stamps
rainData = [allTimeStamps, randi(10, size(allTimeStamps,1),1)];
% Remove some random rows
idx = randi(size(rainData,1),10, 1); %randomized row numbers to remove.
rainData(idx, :) = []; %now we have missing data.
% Detect which time stamps in 'rainData' are in 'allTimeStamps'
matchIdx = ismember(allTimeStamps, rainData(:,1:end-1), 'rows');
% add all NaNs to final column of allTimeStamps, then fill in the data you've got.
allTimeStamps = [allTimeStamps, nan(size(allTimeStamps,1),1)];
allTimeStamps(matchIdx, end) = rainData(:,end);
  4 件のコメント
dpb
dpb 2018 年 7 月 16 日
編集済み: dpb 2018 年 7 月 16 日
Not a link, just used for format appearance...making a joke about the array, only.
Danilo M
Danilo M 2018 年 7 月 16 日
Tks, Adam!

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