gonum.org/v1/gonum v0.16.0: stat.Mean

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:golang/gonum.org/v1/gonum@v0.16.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/gonum.org/v1/gonum@v0.16.0
Demonstrate these symbols/APIs:
  - gonum.org/v1/gonum/stat.Mean

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:bd4d956b544419cdbb46defeb1c0719fce61d9764d40e0a1be711a09183ed88d","contract":["stat.Mean computes the unweighted sample mean of a float64 slice when weights is nil","stat.Mean computes the weighted mean of a float64 slice when weights is provided","stat.Mean panics when the lengths of the data and weights slices do not match","stat.Mean returns NaN when the input data slice is empty"],"goal":"verify pkg:golang/gonum.org/v1/gonum@v0.16.0","kind":"HOW","packages":["pkg:golang/gonum.org/v1/gonum@v0.16.0"],"schemaVersion":1,"symbols":["gonum.org/v1/gonum/stat.Mean"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/gonum.org/v1/gonum@v0.16.0"],"schemaVersion":1,"subject":"pkg:golang/gonum.org/v1/gonum@v0.16.0","symbols":["gonum.org/v1/gonum/stat.Mean"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require gonum.org/v1/gonum v0.16.0

gonum.org/v1/gonum v0.16.0 h1:5+ul4Swaf3ESvrOnidPp4GZbzf0mxVQpDCYUQE7OJfk=
gonum.org/v1/gonum v0.16.0/go.mod h1:fef3am4MQ93R2HHpKnLk4/Tbh/s0+wqD5nfa6Pnwy4E=

package main

import (
	"fmt"

	"gonum.org/v1/gonum/stat"
)

func main() {
	// Sample data
	values := []float64{2.0, 4.0, 4.0, 4.0, 5.0, 5.0, 7.0, 9.0}

	// Calculate unweighted mean
	mean := stat.Mean(values, nil)
	fmt.Printf("Unweighted mean: %.2f\n", mean)

	// Calculate weighted mean
	weights := []float64{1.0, 1.0, 1.0, 1.0, 2.0, 2.0, 1.0, 1.0}
	weightedMean := stat.Mean(values, weights)
	fmt.Printf("Weighted mean: %.2f\n", weightedMean)
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/gonum.org/v1/gonum@v0.16.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/gonum.org/v1/gonum@v0.16.0"
  ],
  "symbols": [
    "gonum.org/v1/gonum/stat.Mean"
  ]
}

package main

import (
	"fmt"
	"math"
	"os"

	"gonum.org/v1/gonum/stat"
)

func main() {
	// Assertion 1: stat.Mean computes the unweighted sample mean of a float64 slice when weights is nil
	data := []float64{1.0, 2.0, 3.0, 4.0, 5.0}
	mean := stat.Mean(data, nil)
	expectedMean := 3.0
	if math.Abs(mean-expectedMean) > 1e-12 {
		fmt.Fprintf(os.Stderr, "FAIL: expected unweighted mean %f, got %f\n", expectedMean, mean)
		os.Exit(1)
	}

	// Assertion 2: stat.Mean computes the weighted mean of a float64 slice when weights is provided
	weights := []float64{1.0, 2.0, 3.0, 2.0, 1.0}
	weightedMean := stat.Mean(data, weights)
	expectedWeighted := 3.0
	if math.Abs(weightedMean-expectedWeighted) > 1e-12 {
		fmt.Fprintf(os.Stderr, "FAIL: expected weighted mean %f, got %f\n", expectedWeighted, weightedMean)
		os.Exit(1)
	}

	asymData := []float64{10.0, 20.0}
	asymWeights := []float64{1.0, 3.0}
	asymMean := stat.Mean(asymData, asymWeights)
	if math.Abs(asymMean-17.5) > 1e-12 {
		fmt.Fprintf(os.Stderr, "FAIL: expected asymmetric weighted mean 17.5, got %f\n", asymMean)
		os.Exit(1)
	}

	// Assertion 3: stat.Mean panics when the lengths of the data and weights slices do not match
	panickedLengthMismatch := false
	func() {
		defer func() {
			if r := recover(); r != nil {
				panickedLengthMismatch = true
			}
		}()
		badWeights := []float64{1.0, 2.0}
		_ = stat.Mean(data, badWeights)
	}()
	if !panickedLengthMismatch {
		fmt.Fprintf(os.Stderr, "FAIL: expected panic on slice length mismatch\n")
		os.Exit(1)
	}

	// Assertion 4: stat.Mean returns NaN when the input data slice is empty
	emptyMean := stat.Mean([]float64{}, nil)
	if !math.IsNaN(emptyMean) {
		fmt.Fprintf(os.Stderr, "FAIL: expected NaN for empty slice, got %f\n", emptyMean)
		os.Exit(1)
	}

	fmt.Println("All gonum stat.Mean contract assertions passed.")
}