How to extract sub-matrices from a big matrix?

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Mohamed Nedal
Mohamed Nedal on 21 Dec 2019
Edited: Stephen on 23 Dec 2019
Hello everyone,
I have two matrices, kindly find the attached file
soho ---> size = 23×12 , each row represents an event.
omni ---> size = 8760 × 17 , each row represent an hour (timeseries data).
The first three columns are, in order, "year", "month", "day".
I need to do the following operation:
if soho_day = omni_day
take that omni_day and the following 120 rows (hours) and put them as a separate matrix with a prefix (i.e., omniSUB_1).
and so on
I have these code blocks
% to find the matched date and store the that day along with the following 5 days (120 hours) in another matrix.
for n = 1:length(soho)
for m = 1:length(omni)
if datetime(soho(n,1),soho(n,2),soho(n,3),...
'Format','dd/MM/yyyy') == ...
datetime(omni(m,1),omni(m,2),omni(m,3),...
Format','dd/MM/yyyy')
for k = m:120
omniSUB{n,:} = omni(k,:);
end
end
end
end
and
% to create sub-matrices.
Prefix = 'omniSUB_';
for i = 1:Month_length
var_name = strcat(Prefix, num2str(i));
data_child = genvarname(var_name);
eval([data_child ' = omniSUB{i}']);
end
but I don't know how to put them together to do that operation. Please correct me.
I appreciate your help.
Thanks in advance
  4 Comments
Mohamed Nedal
Mohamed Nedal on 22 Dec 2019
I'll try the indexing approach. Thanks!

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Accepted Answer

Ridwan Alam
Ridwan Alam on 21 Dec 2019
Edited: Ridwan Alam on 21 Dec 2019
% to find the matched date and store the that day along with the following 5 days (120 hours) in another matrix.
for n = 1:size(soho,1)
omniRowInd = find(omni(:,1)==soho(n,1) & omni(:,2)==soho(n,2) & omni(:,3)==soho(n,3),1,'first');
if ~isempty(omniRowInd)
tempTable = omni(omniRowInd:min(omniRowInd+119,size(omni,1)),:);
eval(['omniSUB_' num2str(n) '=' 'tempTable;']);
end
end
Hope this helps!
  10 Comments
Mohamed Nedal
Mohamed Nedal on 23 Dec 2019
Yes, you're right.
I found where's the error, it was a glitch in defining the date-time pairs and I corrected it.
Thank you!

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