Rules

Anomaly Formula: Percentage-By-Last

What it does:
This rule compares the most recent usage value with the previous one. If the percentage difference between them meets or exceeds your defined threshold, and the direction of change matches your selected type (Increased, Decreased, or Any), an alert is triggered.

When to use it:
Use this formula to detect sudden relative increases or decreases in your usage, especially when absolute changes might seem small but are significant compared to recent patterns.

Examples

✅ Example 1: Increased Usage Triggers Alert

• Anomaly Formula: PercentageByLast
• Change Type: Increased
• Threshold: 40
• History: 100, 105, 110, 115, 200
• Explanation:
  • Previous value = 115, latest = 200
  • Percent change = ((200 – 115) / 115) * 100 = 73.91%
  • It’s an increase, and it exceeds the threshold → ✅ Alert triggered

❌ Example 2: Drop Not Enough to Trigger Alert

• Anomaly Formula: PercentageByLast
• Change Type: Decreased
• Threshold: 35
• History: 80, 78, 76, 75, 60
• Explanation:
  • Previous = 75, latest = 60
  • Percent change = ((60 – 75) / 75) * 100 = -20%
  • It’s a decrease, but below the threshold → ❌ No alert

✅ Example 3: Any Change Type Catches a Drop

• Anomaly Formula: PercentageByLast
• Change Type: Any
• Threshold: 50
• History: 300, 290, 280, 270, 120
• Explanation:
  • Previous = 270, latest = 120
  • Percent change = ((120 – 270) / 270) * 100 = -55.56%
  • Direction is “Any”, and the change exceeds the threshold → ✅ Alert triggered