1. /**
  2. * Flags anomalous timestamps in an array of timestamps.
  3. *
  4. * @param {Array<number>} timestamps An array of timestamp values (e.g., milliseconds since epoch).
  5. * @param {number} anomalyThreshold The number of standard deviations from the mean to consider a timestamp anomalous.
  6. * @returns {Array<number>} An array of indices of anomalous timestamps. Returns an empty array if input is invalid.
  7. */
  8. function flagTimestampAnomalies(timestamps, anomalyThreshold = 3) {
  9. if (!Array.isArray(timestamps) || timestamps.length === 0) {
  10. return []; // Handle invalid input
  11. }
  13. const n = timestamps.length;
  14. if (typeof anomalyThreshold !== 'number' || anomalyThreshold <= 0) {
  15. anomalyThreshold = 3; //Use default if invalid
  16. }
  18. // Calculate the mean and standard deviation
  19. let sum = 0;
  20. for (let i = 0; i < n; i++) {
  21. if (typeof timestamps[i] !== 'number') {
  22. continue; // Skip non-numeric values
  23. }
  24. sum += timestamps[i];
  25. }
  27. const mean = sum / n;
  29. let sumOfSquares = 0;
  30. for (let i = 0; i < n; i++) {
  31. if (typeof timestamps[i] !== 'number') {
  32. continue; // Skip non-numeric values
  33. }
  34. sumOfSquares += Math.pow(timestamps[i] - mean, 2);
  35. }
  36. const stdDev = Math.sqrt(sumOfSquares / n);
  38. // Identify anomalous timestamps
  39. const anomalousIndices = [];
  40. for (let i = 0; i < n; i++) {
  41. if (typeof timestamps[i] !== 'number') {
  42. continue; // Skip non-numeric values
  43. }
  44. const zScore = Math.abs((timestamps[i] - mean) / stdDev);
  45. if (zScore > anomalyThreshold) {
  46. anomalousIndices.push(i);
  47. }
  48. }
  50. return anomalousIndices;
  51. }

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