how to find a value from a timeseries?

13 次查看（过去 30 天）
Tony Castillo
Tony Castillo 2018-7-16
编辑： Guillaume 2018-7-16
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?.
  2 个评论
KSSV
KSSV 2018-7-16
The values are 69.9 and 70, there is no 79 in the data.
Tony Castillo
Tony Castillo 2018-7-16
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

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

KSSV
KSSV 2018-7-16
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)]
  3 个评论
显示 1更早的评论
KSSV
KSSV 2018-7-16
I want to get y values which are equal to 70. So I need to check which values of y are equal to 70 an pick those indices. To compare floating point numbers it is suggested to use abs(y-val)<tolerance. 10^-5 is a tolerance factor, so I am picking those values from y on subtracting from 70, the difference should be less then tolerance.
Guillaume
Guillaume 2018-7-16
编辑：Guillaume 2018-7-16
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.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Logical 的更多信息

标签

产品


版本

R2017a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by