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how to find a value from a timeseries?

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Tony Castillo
Tony Castillo on 16 Jul 2018
Edited: Guillaume on 16 Jul 2018
hi Guys, I got a problem analyzing a time series, because of its length I need to find out a way to obtain the required value without need to scroll all the time series. For instance, how to find from the attached time series the value 79?, it must appear twice in the same time series?. Could you help me?.
Tony Castillo
Tony Castillo on 16 Jul 2018
Oh, I think I have attached the wrong time series, but surely you could check the value 70, it appears twice. How do you do? Thanks in advance

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Accepted Answer

KSSV on 16 Jul 2018
Go for logical indexing:
S = load('soc.mat') ;
t = S.soc.Time ;
y = S.soc.Data ;
idx = abs(y-70)<10^-5 ;
[t(idx) y(idx)]
Guillaume on 16 Jul 2018
Do a search on floating point comparison to learn all about it.
To check that two floating point numbers are equal, you check that there difference is sufficiently small that you can consider them the same. KSSV chose 10e-5 for that sufficiently small difference. It's arbitrary, the value being informed by the magnitude of the numbers and the precision that you require.
Note that you musn't use == to compare floating point numbers, due to the limited precision inheritent to storing floating point numbers on a computer. In particular, a computer will tell you that
(0.1 + 0.1 + 0.1) == 0.3
is false, as computers can't store 0.1 exactly.
Again, do a search to learn more.

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