how to find nearest date and its corresponding value !

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pankaj mali 2019-10-16

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编辑： Andrei Bobrov 2019-10-17

Hi,

I have one date/time array(A). and another mat file (AOD) which has first column of date/time and second column has values.

I need find date/time from (AOD) which is nearest to date/time of (A) and the correspoding values from AOD to that date.

and if it find two dates near to date/time from A(for eg two minutes earlier and two minutes later ). it should take earilier datetime !

In my result matrix I should have first column of date/time from file (A) and second column should be values from AOD which were measured at time somewhere near to date/time first colum !

i hope you understand my question. I am adding those two files here.

pardon my english !

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Turlough Hughes 2019-10-16

Do you want to round the data to the nearest minute in that case?

If you take times in seconds there are no cases where a time in A is midway between two times in AOD.

pruth 2019-10-17

what if i just want to round the data to nearest minute !! How can we do it ?

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Answer 1

Andrei Bobrov 2019-10-16

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load('date.mat');
load('AOD.mat');
d = datetime(A,'ConvertFrom','datenum');
[lo,i] = ismembertol(AOD_440(:,1),A,1,'DataScale',1/8/60);
TT_out = array2timetable(AOD_440(lo,2),'RowTimes',d(i(lo)),'VariableNames',{'data'});

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pankaj mali 2019-10-17

sir, there is one problem in your solution, in the TT_out what i want is all the dates from A and the values from AOD(:,2) which were measure at closest time from A !

I should get the matrix of size

697*2

Andrei Bobrov 2019-10-17

编辑：Andrei Bobrov 2019-10-17

[~,i] = min(abs(AOD_440(:,1) - A(:)));
d = datetime(A,'ConvertFrom','datenum');
TT_out = array2timetable(AOD_440(i,2),'RowTimes',d,'VariableNames',{'data'});

or

T = timetable(AOD_440(:,2),'RowTimes',datetime(AOD_440(:,1),'ConvertFrom','datenum'));
d = datetime(A,'ConvertFrom','datenum');
TT_out = retime(T,d,'nearest');