Reject Zero Division

Review ask

As a clinical trial statistician or programmer, challenge anything in this benchmark: describe a problem in Comments, or propose a fix with the Edit button on any source file.

Task: Is this a specification error a study team could realistically make, and should the build stop on it rather than continue?
Inputs: Do they trigger the failure for the reason the summary gives?
Expected failure: Is this the right error, raised at the right point, and would it tell the programmer what to fix?

The other tabs beside Comments are background for assessment, not under review.

Summary

EditUnder reviewWhat this benchmark means

README.md

Goal: work out PCHG, the percent change from baseline, from the collected result in AVAL and its baseline in BASE.

Input: laboratory results with baseline values from LB, carrying the collected numeric result (LBSTRESN) and the baseline it is compared with (LBBLRESN).

Variables:

AVAL would be the collected numeric result, taken from LBSTRESN.
BASE would be the baseline it is compared with, taken from LBBLRESN.
PCHG would be the change from baseline as a percentage of it, worked out as 100 * (AVAL - BASE) / BASE; missing when either value is missing.

Note: a zero baseline leaves the percentage with no value. Leaving it missing would assume a rule the request never stated, so the run fails and no artifact is accepted.

How to fix

If the intended result is missing when BASE is zero, guard the denominator explicitly with NULLIF:

derivation:
  compute:
    expr: "100 * (AVAL - BASE) / NULLIF(BASE, 0)"

NULLIF(BASE, 0) returns missing for a zero baseline. Missing then propagates through the division, so PCHG is missing for that row instead of raising division_by_zero; nonzero baselines retain the original calculation.

Expected failure

Editthe run is rejected; no artifact is accepted

expected/error.yaml

phase: derivation
condition: division_by_zero
requirement: REQ-0430

expected/error.yaml

phase: derivation
condition: division_by_zero
spec_paths:
  - columns.PCHG.derivation.compute
requirement: REQ-0430
context:
  expr: "100 * (AVAL - BASE) / BASE"
  keys:
    - STUDYID: PILOT7
      USUBJID: P7-742
      PARAMCD: ALT

YAML specification

1 spec file

spec.yaml

Edit44 lines

1schema_version: "1.0"2domain: ADLB3keys: [STUDYID, USUBJID, PARAMCD]4input:5  LB: input/lb.csv67output:8  path: adlb.csv9  columns: [STUDYID, USUBJID, PARAMCD, AVAL, BASE, PCHG]1011columns:12  - name: STUDYID13    type: str14    label: Study Identifier15    derivation: LB.STUDYID1617  - name: USUBJID18    type: str19    label: Unique Subject Identifier20    derivation: LB.USUBJID2122  - name: PARAMCD23    type: str24    label: Parameter Code25    derivation: LB.LBTESTCD2627  - name: AVAL28    type: float29    label: Analysis Value30    derivation: LB.LBSTRESN3132  - name: BASE33    type: float34    label: Baseline Value35    derivation: LB.LBBLRESN3637  - name: PCHG38    type: float39    label: Percent Change from Baseline40    # Missing when AVAL or BASE is missing. A zero BASE stops the run with41    # a division by zero, since no rule says what the result should be.42    derivation:43      compute:44        expr: "100 * (AVAL - BASE) / BASE"

Inputs

Under review1 source file

input/lb.csv

Edit2 rows

input/lb.csv
STUDYID	USUBJID	LBTESTCD	LBSTRESN	LBBLRESN
PILOT7		ALT	42	35
PILOT7		ALT	38	0

Unexpected Output

Under reviewNo artifact is produced

No fixture files in this directory.

Shaded columns are derived— = missing value

Comments and assessment materials

Dataset Name	Variable Name	Variable Label	Type	Computational Method	Origin
ADLB	STUDYID	Study Identifier	character	Copy value from LB.STUDYID.	Predecessor
ADLB	USUBJID	Unique Subject Identifier	character	Copy value from LB.USUBJID.	Predecessor
ADLB	PARAMCD	Parameter Code	character	Copy value from LB.LBTESTCD.	Predecessor
ADLB	AVAL	Analysis Value	numeric	Copy value from LB.LBSTRESN.	Predecessor
ADLB	BASE	Baseline Value	numeric	Copy value from LB.LBBLRESN.	Predecessor
ADLB	PCHG	Percent Change from Baseline	numeric	Compute 100 * (AVAL - BASE) / BASE.	Derived

Version	Date	Author	Description
1.3	2026-09-29	yamaa docs build	Show study codelist names, external dictionaries, and ISO 8601 formats in variable rows; list the document's codelist values and metadata
1.2	2026-09-29	yamaa docs build	Classify ADaM copies from a declared input as Predecessor and recodes as Derived, and SDTM recodes of locally derived columns as Derived
1.1	2026-09-29	yamaa docs build	Resolve lookups into the donor record they select, and give every derivation shape a plain-language rule instead of its raw YAML
1.0		yamaa docs build	Initial generation from spec.yaml

How to fix

input/lb.csv

Comments

Mapping spec