在一维数组中查找时间序列数据中的波峰和波谷-Javascript

Question

So basically i have a 1d array with over 500 values floating between the ranges of 100- 130 or about there arranged in no particular order(its random); and I wanna know how can I find the peaks and troughs of this data. Is there a way to also change sensitivity of the peak detection? What is a comprehensive algorithm for this? If there is a JS library for it, that would be awesome.

Answer 1

An algorithm for finding peaks and troughs would be essentially the same thing you would do with your finger when looking at a graph. You go from the start and follow the line and take note when you see a peak and a trough.

Programmically we can define that as this:

For some array of length n ( with n-1 being the index of the last element and 0 the index of the first ), iterate thorough from 1 to n-2 . Then peaks and troughs would be defined as:

• For element i , if i-1 > i and i+1 > i . Then i is a trough.
• For element i , if i-1 < i and i+1 < i . Then i is a peak.

This would be an O(n) algorithm and be enough information to be able to program it.

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Below is an example program implementing the algothim above:

 var array = [102,112,115,120,119,102,101,100,103,105,110,109,105,100]; function findPeaksAndTroughs(array) { var start = 1; // Starting index to search var end = array.length - 2; // Last index to search var obj = { peaks: [], troughs: [] };// Object to store the indexs of peaks/thoughs for(var i = start; i<=end; i++) { var current = array[i]; var last = array[i-1]; var next = array[i+1]; if(current > next && current > last) obj.peaks.push(i); else if(current < next && current < last) obj.troughs.push(i); } return obj; } console.log(findPeaksAndTroughs(array));