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how can i extract data of specific dates in a big excel file and save in a different excel file?

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KIPROTICH KOSGEY
KIPROTICH KOSGEY 2019-10-31
回答： Mir Amid Hashemi 2019-11-4
Hi,
Please i would like to extract data of some specific dates in the output file (data.xlsx) of the following function, and save in another excel file (data1.xlsx). Can someone please help?
y0=[0.02352;0.00048;0.0288;0.00432;0.216;0.1104;0.1104;2;2;2;55;50;0.5];
h=0.0006944444;
tSpan=0:h: 535;
M=[ 1 0 0 0 0 0 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0 0 0 0 0
0 0 0 1 0 0 0 0 0 0 0 0 0
0 0 0 0 1 0 0 0 0 0 0 0 0
0 0 0 0 0 1 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0 0 0 0 0 0
0 0 0 0 0 0 0 1 0 0 0 0 0
0 0 0 0 0 0 0 0 1 0 0 0 0
0 0 0 0 0 0 0 0 0 1 0 0 0
0 0 0 0 0 0 0 0 0 0 1 0 0
0 0 0 0 0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 0 0 0 0 0 1];
options = odeset('RelTol',eps^20,'AbsTol',1e-2, 'Mass', M);
[tSol, ySol]=ode23t(@(t, y) MBBRFun5(t,y), tSpan, y0, options);
xlswrite('F:\Matlab\data.xlsx',[tSol, ySol]);
I would like to extract data for t=4, 6, 7, 9.... etc in data.xlsx
Thanks in advance
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Bob Thompson
Bob Thompson 2019-10-31
What does t actually represent other than different values of tspan. I know I spoke about t(4) earlier, but from what I understand of your code, t(4) doesn't actually exist because t is a temporary assignment from tspan. If you want the four value of t use tspan(4).
vals = [4 6 7 9 ...]; % Identify the indices you want
tspan(vals); % This is the values you want

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Mir Amid Hashemi
Mir Amid Hashemi 2019-11-4
It might be useful to use Tall Arrays. These arrays are not completely loaded into memory if they are really big.
I would recommend to go to https://uk.mathworks.com/help/matlab/import_export/tall-arrays.html
Amid.

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