MATLAB: Matching string from multiple arrays

Hi,

I have three structures with time stamps (char arrays, eg '2016-11-02 10:00:00') and corresponding datapoints of significant wave heights (double), and these are of different length for the three structures so I cannot just concatenate them.

Basically I want to make a new array with only the datapoint values where the correcpodning time stamp exists in all three of my structures' time stamp field .

I've used ismember and matrix multiplication for just two of the structures (see below), but I realise that I still have values in the array I'm checking against that doesn't exist in the thing I'm checking, so I still have uneven lengths of the arrays. I have 163 triplets of stuctures to check, hence the 'i' to be able to run through all of them eventually.

Drifter_okera5 = ismember(cellstr(Drifters(i).ObsTimestamp), cellstr(era5(i).timestamp)); % check if what is in drifters are in era5
DrifterHsera5 = Drifter_okera5.*Drifters(i).Hs'; % Take the resulting logical matrix and multiply it with the drifter HS
DrifterHsok = DrifterHs(DrifterHs~= 0); %remove all the values that are now zeros, these do not have a matching era5 hs

Any tips are most welcome!

% Create demo data - all column vectors A.timestamp = datetime(2020,1,1)+days(1:10)'; A.waveheight = rand(10,1); B.timestamp = datetime(2020,1,1)+days(1:15)'; B.waveheight = rand(15,1); C.timestamp = datetime(2020,1,1)+days(1:5)'; C.waveheight = rand(5,1); % Find which datetime values *exactly* match in all 3 structures. % dtInAll is a vector of datetime values that exist in all 3 strcutures. dtInAll = intersect(intersect(A.timestamp,B.timestamp),C.timestamp);

% waves is a nx3 matrix of waveheights where columns are defined by % [A,B,C] structures and rows defined by deInAll. waves = [A.waveheight(ismember(A.timestamp, dtInAll)), ... B.waveheight(ismember(B.timestamp, dtInAll)), ... C.waveheight(ismember(C.timestamp, dtInAll))];

T = table(); T.TimeStamp = dtInAll T = [T, array2table(waves,'VariableNames',{'A','B','C'})]; % 5×4 table % TimeStamp A B C % ___________ _______ ________ _______ % 02-Jan-2020 0.94479 0.40391 0.64775 % 03-Jan-2020 0.49086 0.096455 0.45092 % 04-Jan-2020 0.48925 0.13197 0.54701 % 05-Jan-2020 0.33772 0.94205 0.29632 % 06-Jan-2020 0.90005 0.95613 0.74469

Best Answer

Here's a demo that identies exact datetime matches. It assumes you've already converted the timestamps to datetime values instead of char using t = datetime(DateStrings,'InputFormat',infmt).

Now you can get the indices of datetime matches for each structure and extract the waveheight values.

Summarize the resuls in a table (or timetable)