Extract consecutive data points between 2 thresholds

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Joshua Pretorius
Joshua Pretorius 2021-9-7
评论： Joshua Pretorius 2021-10-5
For a project, i have data in the form of wind speed (m/s) recorded with 1 minute intervals, starting from 2009 through to 2021. For the time of each recording I have created a datetime array in the form of yyyy:MM:dd_HH:mm:ss, and for the wind speed recorded at each minute i have created a double array.
The wind speed ranges from 0 through to 40+ m/s. For the project, any wind speeds above 30m/s will cause damage to some machinery and hence, occurances where windspeed exceeds 30m/s must be recorded. Additionally, for each case where wind speed data exceeds 30m/s, i need to find the time taken (in minutes based on the datetime data) for the wind speed to go from 20m/s to the 30m/s limit. So the extracted data points between 20 and 30 m/s must be consequtive, which will allow me to find the time taken for cases where wind speed gradually increases from 20 to 30 m/s. Im not too fussed on the method used to extract the data with said conditions, so any sort of direction/help would be greatly appreciated.
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Walter Roberson
Walter Roberson 2021-9-8
Should there be a sliding window (what width?) in which the condition is set true if mean() over the window is > 30, or median() over the windows is > 30, or if count of (data>30) is > 1 ?
Joshua Pretorius
Joshua Pretorius 2021-10-5
Hi Walter, sorry for the late reply.
Im able to use a moving average to smoothen the data set and get rid of instances where the wind speed quickly drops below the threshold. Based on different trials, a moving average of 5-10 does a good job.

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回答（1 个）

KSSV
KSSV 2021-9-7
Let t be your dates in datetime format and w be your wind data.
% get indices of wind lying in [20, 30]
idx = w>= 20 & w <= 30 ; % results into logical indexing
t1 = t(idx) ; % extract those dates
w1 = w(idx) ; % extract the wind data
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Walter Roberson
Walter Roberson 2021-9-7
This does not handle the idea that the points must be consecutive.
KSSV
KSSV 2021-9-7
From the obtained dates, calculate the diff, wherever diff is 1, those indices can be picked.

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