← All workshopsRead Finding Unusual Readings Without Letting Them Set the Reference

Anomaly Detection

Score new pressure readings

BOTIE

Take the median absolute distance of reference readings from their own median.
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0 passed · 0 failed · 2 not run

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Examples, experiments and workspace controls
Live values

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Use a copy of the example to try your own data. Keep the problem's assumptions in mind, and predict the effect of a change before checking the output. You can also add another branch to compare two ways of doing the calculation.

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Context for this challenge

Take the median absolute distance of reference readings from their own median.

Botie has reference records and separate incoming readings.

Inspect the component calculation
Median of a list(
  Reference values: Absolute value(
    Difference: Subtract(
      Starting value: Reference readings
      Value to remove: Median of a list(
        Reference values: Reference readings
      )
    )
  )
)
Examples and results
Reference readings
  1. 08
  2. 19
  3. 210
  4. 311
  5. 4100
Required result
1
Reference readings
  1. 00
  2. 12
  3. 24
Required result
2
Try a fresh construction

This clears this draft, including its undo history. Earlier successful attempts stay recorded. Build again without opening hints to record an independent attempt.

Stuck? Inspect a worked construction

The tools below form one possible solution. You can assemble it, follow its signals, and undo that change to return to your own construction.

Assumptions and test precision

Requires positive MAD. A large score indicates unusualness, not a diagnosed fault. Numerical tests allow a difference of 0.001. Lists and structures must also have the right shape.

Your last tested pieces can start the full construction. An existing draft there keeps its own pieces.

A distant reference value does not set the centre

This check uses the pieces from “Keep the reference centre and spread on their own branch”.

BOTIE

Botie's reference readings include one very large observation. Calculate each new reading's absolute distance from the reference median, divided by the reference median absolute deviation. Use the raw MAD without a normal-consistency multiplier.
Reference readings
  1. 010
  2. 112
  3. 214
  4. 316
  5. 4100
Incoming readings
  1. 08
  2. 114
  3. 226

Use a number, text, or an array matching the requested result. For a matrix, put each row in brackets. Saving your prediction runs your current construction on these inputs and checks the earlier examples too.

Build a construction in the workspace above first. This case will test those pieces.

What would a large score justify checking before declaring a sensor faulty?

Unusualness is evidence for investigation, and a zero MAD needs an explicit reference policy.

Requires positive MAD. A large score indicates unusualness, not a diagnosed fault.

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Continue the courseJudging a Reading Against Its Neighbours →
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