How to interpolate under specific condition?

조회 수: 4 (최근 30일)
Daphne PARLIARI . 2021년 1월 13일
댓글: Daphne PARLIARI . 2021년 1월 14일
Hi everyone. I would appreciate your help on this.
I have a daily timeseries of temperature observations for 2006-2016.
I want to reconstruct missing values (see attached) with an interpolation method only if the missing values cover less that 3 days. If the gap is larger (>4days), I want NaN values to be preserved. Column A contains the dates I have temperature observations (NaT indicates temperature is NaN) and Column C is the full time sequence 2006-2016.
How can I do this? I am totally confused... The interpolation method could be anything, I have not decided on this yet.
Thank you in advance!
PS. I am on R2019a.

채택된 답변

Stephan Ciobanu
Stephan Ciobanu 2021년 1월 13일
편집: Stephan Ciobanu 님. 2021년 1월 13일
Hi, this code should work:
The file Daily data.xlsx must be in the same directory as your script!
DATA = importdata('Daily data.xlsx'); % importing all data
MeanTemp =; % creating an array containg the mean Temp measured
pos = find(isnan(MeanTemp)); % find NaN elements
x_val = (1:length(MeanTemp))'; % creatin a 'pseudo-timeline' vector
for i = 4:length(pos) % finding the index of 4 or more consecutive NaN
if (pos(i)==pos(i-2)+2 && pos(i)==pos(i-1)+1 && pos(i)==pos(i-3)+3)
consec_nan = find(consec_days==true); % index of pos where we want to keep NaN
y = pos;
y(consec_nan-3) = 0;
y(consec_nan-2) = 0;
y(consec_nan-1) = 0;
y(consec_nan) = 0;
k = find(y==0); % excluding 4 or more consecutive days in interpolation
y(k)=[]; % NaN to be interpolated
MeanTemp(pos)=[]; % values to be interpolated
x_unknown_temp = [x_val;y];
x_unknown_temp = sort(x_unknown_temp);
MeanTemp_interpolated = spline(x_val,MeanTemp,x_unknown_temp);
MeanTemp_interpolated1 = interp1(x_val,MeanTemp,x_unknown_temp);
% Creating a matrix with 2 rows
% containg the values of NaN interpolated
% in both cases
% (spline first column, interp1 second column)
Values_interpolated(:,1) = MeanTemp_interpolated(y);
Values_interpolated(:,2) = MeanTemp_interpolated1(y);
% Date-time line below:
datetime1 = datetime(2006,01,01):caldays(1):datetime(2016,12,31);
% String_Values_interpolated contains Values_interpolated
% and the relative day
String_Values_interpolated = num2cell(Values_interpolated(1:end,1:2));
String_Values_interpolated(:,3) = cellstr(datetime1(y))';
  댓글 수: 5
Daphne PARLIARI 2021년 1월 14일
I am sorry, where should I add the script above?

댓글을 달려면 로그인하십시오.

추가 답변 (1개)

Steven Lord
Steven Lord 2021년 1월 14일
If you were using release R2020b or later, I would recommend calling the fillmissing function with the 'MaxGap' option. I'm leaving this as an answer even though you're using release R2019a for future reference by other users or in case you can and are willing to upgrade.
  댓글 수: 1
Daphne PARLIARI 2021년 1월 14일
Yes you are absolutely right. MaxGap doesn't work for me but it is exactly what I need.

댓글을 달려면 로그인하십시오.


Help CenterFile Exchange에서 Interpolation에 대해 자세히 알아보기

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by