Elamur Groupantsmlab-builtins-stats-descriptive
The groupant beside mlab/src/builtins/stats.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial | approximant |
| ast | partial | ../syntax.json |
| cost | symbolic source derived | invariant |
| descriptant | present | descriptant |
| invariant | partial | invariant |
| tests | partial bounded parent evidence | tests |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
behavior_complement | behavior_complement | partial source derived model | behavior_complement |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
quantile_coordinates | quantile_coordinates | partial source derived model | quantile_coordinates |
covariance_policy | covariance_policy | partial source derived model | covariance_policy |
branch_relation | branch_relation | partial source derived model | branch_relation |
resource_cost | resource_cost | partial source derived model | resource_cost |
Model text
descriptant
mlab-builtins-stats-descriptive
quantile cleans NaNs, sorts then interpolates pos=np+.5 with endpoints clamped; mode delegates table agg. moments drops NaN, covariance does not. cov scalar0/1 second arg treated normalization when first numel>1. histogram final edge included in last bin.
Epoch 2026-10-31: isolated source-bound fragment over bytes [7891,15577); includes no claim beyond this relation. Source hash bdc3772b09d9113e108afa29e391fee97a5372caf9052bb1689996c41c94116f.
approximant
descriptive: forward relation
quantile cleans NaNs, sorts then interpolates pos=np+.5 with endpoints clamped; mode delegates table agg. moments drops NaN, covariance does not. cov scalar0/1 second arg treated normalization when first numel>1. histogram final edge included in last bin.
Domain: Finite, well-shaped bounded observations unless branch explicitly describes NaN/Inf. Direct public chi2/OLS helpers assume dimensions not checked at every index; wrappers add validation.
Executable surrogate gap: no measured cheaper implementation with a useful scoped metric is supplied. Categorical/error/effect relations are exact obligations, not percent losses. Future numeric caps only1/2/5/10%.
invariant
descriptive: invariant and cost
s=[1,3], p=.5 gives2; p=0 gives1; empty givesNaN.
N or N-1 denominator selected by cov weight; constant diagonal corrcoef forced1, off-diagonal mayNaN.
Scope-specific cost: Quantile/mode O(n log n), moments O(n), covariance O(n*p²), histogram O(n log bins) using partition_point, storage O(n+p²).
models
behavior_complement
NaN-clean moments cannot reconstruct missing count. corrcoef empty produces NaN; this does not guarantee cov empty safety (cs[0]). Invalid quantile probabilities fail before sorting.
reverse_reconstruction
Quantiles admit sorted arrays sharing interpolated positions and arbitrary source permutations/NaNs. Covariance admits translated observation sets and rotational symmetries.
quantile_coordinates
s=[1,3], p=.5 gives2; p=0 gives1; empty givesNaN.
covariance_policy
N or N-1 denominator selected by cov weight; constant diagonal corrcoef forced1, off-diagonal mayNaN.
branch_relation
quantile cleans NaNs, sorts then interpolates pos=np+.5 with endpoints clamped; mode delegates table agg. moments drops NaN, covariance does not. cov scalar0/1 second arg treated normalization when first numel>1. histogram final edge included in last bin.
resource_cost
Quantile/mode O(n log n), moments O(n), covariance O(n*p²), histogram O(n log bins) using partition_point, storage O(n+p²).
tests
Evidence boundary
See ../tests.md for the actual selected source test and mutant. These tests sample the file, not every fragment branch. NaN-clean moments cannot reconstruct missing count. corrcoef empty produces NaN; this does not guarantee cov empty safety (cs[0]). Invalid quantile probabilities fail before sorting. Other branches here are source-derived and unexecuted unless the parent test explicitly calls them.
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