Library/Fundamental Analysis and Valuation/Relative Valuation/P/E Comparable Valuation

D18-F03-A01 / Complete engineering topic

P/E Comparable Valuation

Build an auditable P/E comparable valuation that exposes every peer multiple, the median selection, dispersion, and the target-price bridge.

P/E Comparable Valuation maps eligible peer fundamentals to an auditable relative valuationD18 / D18-F03

Build an auditable P/E comparable valuation that exposes every peer multiple, the median selection, dispersion, and the target-price bridge.

P/E Comparable Valuation turns eligible peers into a conditional, auditable value

Figure 1. Synthetic canonical path from declared peer inputs to the selected relative-value output; the estimate is conditional, not intrinsic or predictive.

The decision this tutorial makes visible

P/E is easy to type and easy to misuse. Trailing versus forward earnings, basic versus diluted EPS, one-off items, losses, forecast vintage, and peer selection can change the answer before any multiplication occurs.

The precise question is: What price per share follows when a target's positive EPS is valued at the median P/E of an eligible peer set?

A practitioner needs to know what the diagnostic does and does not justify. A builder needs a contract that can be reproduced from the same point-in-time inputs in Python, TypeScript, a visual, and a browser lab.

Intuition before notation

Each peer converts one unit of earnings into an observed equity price. The median supplies a robust central conversion rate; target EPS then converts that rate back into a per-share value.

The result depends on the declared algorithm scope, input clocks, units, equality and rounding policies, and unsupported-state treatment. Change one of those and the output represents a different decision even when its field name is unchanged.

Scope and nearby methods

The canonical variant uses positive, consistently normalized EPS for the target and at least three peers, selects the ordinary median peer P/E, and multiplies it by target EPS. Mean, harmonic-mean, relative-P/E, and negative-earnings variants are outside this exact contract.

VariantDefinitionBest useMain limitation
Canonical median positive-EPS P/EMedian peer P/E × target EPSTransparent public compsLoss firms are out of scope
Forward P/EPrice divided by forecast EPSForward-looking comparisonEstimate revisions
Harmonic or aggregate P/EAlternative aggregation of earnings yieldsIndex or portfolio contextsDifferent statistic and interpretation

What is sourced, selected, synthetic, and derived

RoleMaterial claimEvidenceBoundary
Sourced factComparable-firm selection changes P/E valuation accuracy.Alford (1992)Sample evidence does not guarantee a new peer set.
Implementation choiceUse the ordinary median of positive peer P/Es.Frozen package contractNot a universal valuation standard.
Synthetic teaching inputThe median peer P/E is 18× and target EPS is 2.40.Repository fixtureNot market data.
Author-derived calculationThe implied price is 43.20.18 × 2.40Conditional on peer eligibility and normalization.

The authoritative sources support only the exact facts named in the claim ledger. They do not certify the synthetic numbers in this tutorial. The repository fixture is deliberately invented for auditability, and the displayed output is author-derived under the selected implementation choice.

Formula, symbols, and numerical policy

Plain text
PE_i = Price_i / EPS_i; selected_PE = median(PE_i); implied_price = selected_PE × target_EPS
SymbolMeaningUnitPolicy
P_ipeer pricecurrency/sharesame share class and timestamp basis
EPS_inormalized peer EPScurrency/sharestrictly positive
m_PEselected median P/Eturnsno weighting
P*target implied pricecurrency/sharenot a forecast
  • Use IEEE-754 binary64 arithmetic without intermediate rounding.
  • Report ratios to at least four decimals and currency outputs to a declared presentation precision only after calculation.
  • Use the ordinary median; for an even peer count, average the two central values.
  • Keep percentage points distinct from decimals and basis points.

Read the formula in the same order as the algorithm. Validate identity, ordering, units, and supported state first. Apply the selected equality and window rules second. Calculate with unrounded numeric values. Round only at the declared presentation boundary, and preserve null as a diagnostic rather than coercing it to zero.

Build the algorithm

  1. Freeze valuation date, EPS horizon, share class, and knowledge cutoff
  2. Validate positive target and peer EPS
  3. Calculate every peer P/E
  4. Inspect range and choose the ordinary median
  5. Multiply median P/E by target EPS
  6. Compare with current price without treating the gap as expected return

Production-minded operational checklist

  1. Freeze valuation and knowledge-cutoff timestamps.
  2. Reconcile every numerator and denominator to a declared reporting basis.
  3. Apply eligibility rules before aggregation.
  4. Inspect peer dispersion and sensitivity before using a point estimate.
  5. Store the complete peer ledger beside the result.

The checklist is intentionally strict: an explicit rejection is safer than a plausible output built from stale, malformed, or unsupported state.

Worked synthetic example

The canonical fixture is synthetic teaching data, not an observed control event, customer order, or broker execution. Its primary author-derived output, implied_price, is 43.2. The complete input and output are in datasets/canonical-input.json and datasets/expected-output.json.

Synthetic peer P/Es are 14×, 16×, 18×, 20×, and 22×. The median is 18×. Multiplying by target EPS of 2.40 gives 43.20, which is 8% above the synthetic current price of 40.00.

Canonical peer audit table

Synthetic peerDerived PE RATIO
P114.0000×
P216.0000×
P318.0000×
P420.0000×
P522.0000×
Selected median18.0000×

The table is the calculation ledger—not a market sample. Recalculate it before changing any displayed value.

Counterfactual checkpoint

Loss boundary. If target EPS becomes zero or negative, the package rejects P/E instead of returning infinity or a negative multiple. The output changes because the ordered positive-multiple interpretation has failed

The structured result retains state and diagnostics in addition to the primary number. That makes the calculation independently reviewable and prevents a partial, null, rejected, or venue-bounded outcome from being mistaken for an unqualified value.

Boundary and counterexample workbook

The playground computes every scenario at 61 deterministic parameter states. The table uses the declared focus step and states whether that focus reproduces the canonical fixture. The full state ledger and compressed transition segments are in datasets/scenario-results.json.

ScenarioReview focusPurposeStatePrimary outputDiagnosticDecision segments
Canonical driver sweepStep 30 · canonical fixtureSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete43.2000 implied priceselected 18.0000× · peer range 8.0000× · valuation-complete1
Peer dispersionStep 30 · comparison focusSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete48.0000 implied priceselected 20.0000× · peer range 8.5000× · valuation-complete1
Peer valuation levelStep 30 · canonical fixtureSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete43.2000 implied priceselected 18.0000× · peer range 8.0000× · valuation-complete1
Current-price comparisonStep 30 · comparison focusSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete43.2000 implied priceselected 18.0000× · peer range 8.0000× · valuation-complete1
Denominator edgeStep 30 · comparison focusSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete22.0500 implied priceselected 18.0000× · peer range 8.0000× · valuation-complete1
Target fundamental sensitivityStep 30 · comparison focusSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete48.6000 implied priceselected 18.0000× · peer range 8.0000× · valuation-complete1
Stress comparisonStep 30 · comparison focusSynthetic deterministic scenario; every state is recomputed from the reference algorithm.valuation-complete38.4000 implied priceselected 16.0000× · peer range 8.0000× · valuation-complete1

These rows are not backtest observations. They are controlled counterexamples that expose how one driver changes the state, output, or reason code while the rest of the contract stays fixed.

Visualize the boundary

Calculation flow

Rendering system map…

The flow is deliberately gated: a failed input, eligibility, unit, or model-design check stops the value bridge instead of silently manufacturing a number.

P/E Comparable Valuation annotated teaching map

P/E Comparable Valuation calculation, routing, and rejection decisions

Figure 3. Unsupported states are routed or rejected explicitly instead of being converted into a plausible-looking multiple.

Open this SVG at full size, or use the guided playground to compare the seven topic-specific canonical, boundary, policy, and failure scenarios.

The Mermaid flow answers where the selected calculation sits in the processing sequence. The SVG keeps the formula, output, decision boundary, and invariant visible together. The lab lets the reader step through the same structured states without changing the underlying definition.

Implementation walkthrough

The Python and TypeScript references begin with the same validation contract, reject malformed and unsupported state before calculation, preserve declared ordering and rounding policies, and return structured diagnostics rather than one context-free number.

The main implementation branches are:

  • Target or peer EPS ≤ 0 — Reject or route to another multiple, because Negative P/E is not ordered like an ordinary positive multiple.
  • Peer P/E is extreme — Retain only if economically and data comparable; show dispersion, because Median is robust but not a substitute for investigation.
  • Trailing and forward EPS are mixed — Reject, because The denominators describe different information sets.

Neither reference silently fetches data, mutates caller-owned inputs outside the declared engine behavior, guesses hidden state, or substitutes a provider default. Shared JSON fixtures make value, null, state, and reason-code drift visible across languages.

Testing and validation

Definition tests compare every canonical field, reject malformed state, and exercise the material boundary. Family validation recomputes every playground state from the reference function. Independent arithmetic is recorded beside the fixture rather than inferred only from implementation output.

The audit must preserve these invariants:

  • every eligible peer's raw numerator and denominator
  • each derived peer multiple
  • selected aggregation statistic and dispersion
  • target denominator and capital bridge
  • final implied value and comparison with current price

Passing the suite proves selected-convention arithmetic and cross-language parity; it does not prove peer comparability or investment usefulness.

Failure modes and misuse

  • The selected peer statistic transmits peer mispricing and normalization errors into the target estimate.
  • A narrow range does not prove economic comparability; a wide range makes the point estimate fragile.
  • Forward inputs are estimates with provider, vintage, horizon, and revision risk.
  • Relative valuation explains a price conditional on peer pricing; it does not establish intrinsic value or future return.

Debugging order

When a result looks surprising, inspect the state in this order:

  1. Confirm identifiers, scope, side, and decision clock.
  2. Confirm units, ordering, and point-in-time inputs.
  3. Confirm equality, rounding, null, and reset policies.
  4. Recalculate the invariant and declared scenario focus before changing code.

Evidence and historical boundary

Historical decision: not useful. A named company would add filing identity, provider-price, forecast-vintage, adjustment, licensing, and hindsight questions without clarifying the arithmetic better than controlled synthetic peers. The package therefore makes no claim about any real security's fair value or future return.

The primary sources are Damodaran relative valuation, NYU valuation portal, Alford (1992). They support the source roles listed in the research ledger, not a redistributable historical observation, a private participant decision, production conformance certification, execution-quality result, profitability claim, or prediction claim.

<!-- D18-F03 additive enhancement: method-selection and continuity -->

Choosing among the five relative-value methods

Use the value basis to choose the method before looking at the output label. The highlighted row is this topic's frozen contract; the other rows are nearby methods, not interchangeable fallbacks.

MethodValue basisCanonical driverRejection or routing boundary
P/E Comparable ValuationEquity value / sharePositive EPSReject nonpositive EPS
EV/EBITDA Comparable ValuationEV to equity bridgePositive EBITDARoute financial firms; reject incompatible EBITDA
Price-to-Book ValuationEquity value / sharePositive common BVPSReject nonpositive book; no silent tangible-book swap
PEG RatioForward P/E / growth pointPositive growth pointsReject zero/negative growth; expose 100 times unit trap
Peer-Multiple RegressionConditional fitted multipleGrowth plus ROE plus leverageReject small/rank-deficient designs; flag extrapolation

Interpretation ladder for P/E Comparable Valuation

  1. Ask: What price per share follows from an eligible peer P/E median?
  2. Verify the driver: Positive EPS.
  3. Preserve the basis: Equity value per share.
  4. Stop or route when: Reject nonpositive peer or target EPS.
  5. Carry the result forward only as conditional relative value, with its valuation date, knowledge cutoff, units, peer ledger, and diagnostic state.

P/E Comparable Valuation method-selection map showing five non-interchangeable relative-value contracts

Figure 4. The highlighted contract answers this topic's question; the other rows prevent a familiar multiple from being applied to the wrong denominator or value basis.

The companion topic glossary defines governed terms and units. Continue through the family learning flow, then use the embedded playground to test the same boundary under synthetic scenarios.

Summary and next topic

You can now produce an auditable equity-value multiple estimate. The learning flow is: Normalized financial statements and peer universe → P/E Comparable Valuation → EV/EBITDA Comparable Valuation. Carry the result forward only with its scope, clock, state, and evidence label.

P/E Comparable Valuation calculation flow

This flow identifies the selected calculation stages and the structured output.

Rendering system map…

Takeaway: The multiplication is the last step; eligibility, basis, and dispersion determine whether it means anything.

ReferencesPrimary sources and evidence notes

Expand the source trail, evidence role, and limitations behind the engineering choices.

S1 — Relative Valuation

  • Organization or authors: Aswath Damodaran, New York University Stern School of Business
  • Source type: Authoritative academic lecture material
  • Publication or effective date: Current teaching deck accessed 2026-08-04
  • Version: 91-page relative-valuation deck
  • URL or DOI: https://people.stern.nyu.edu/adamodar/pdfiles/country/relval.pdf
  • Accessed: 2026-08-04
  • Jurisdiction: General corporate valuation
  • Supports: A multiple must be defined consistently, compared across genuinely comparable firms, and controlled for growth, risk, and cash-flow fundamentals.
  • Limitations: Does not prescribe this package's synthetic peers, median selection, or point estimate.

S2 — Valuation: Relative Valuation Resources

  • Organization or authors: Aswath Damodaran, New York University Stern School of Business
  • Source type: Authoritative academic resource index
  • Publication or effective date: Accessed 2026-08-04
  • Version: Current web page
  • URL or DOI: https://pages.stern.nyu.edu/~adamodar/New_Home_Page/valuation/val.htm
  • Accessed: 2026-08-04
  • Jurisdiction: General corporate valuation
  • Supports: P/E, PEG, value/EBITDA, and price/book are distinct relative-valuation multiples with distinct fundamental drivers.
  • Limitations: The page is a resource index, not a standardized data contract.

S3 — The Effect of the Set of Comparable Firms on the Accuracy of the Price-Earnings Valuation Method

  • Organization or authors: Andrew W. Alford
  • Source type: Original peer-reviewed research
  • Publication or effective date: 1992
  • Version: Journal of Accounting Research 30(1), 94-108
  • URL or DOI: https://doi.org/10.2307/2491093
  • Accessed: 2026-08-04
  • Jurisdiction: Empirical listed-equity sample
  • Supports: Comparable-firm selection affects P/E valuation accuracy and can be studied by industry, risk, and earnings growth.
  • Limitations: Does not guarantee accuracy for a new sample or endorse the package's synthetic peer set.

Evidence boundary

Sources establish the valuation concepts, accounting or regulatory boundaries, and research context. They do not verify the synthetic fixture, select these peers, or support a return forecast.

relative-valuation.ts
/** Reference calculations for D18-F03 Relative Valuation. */

type Row = Record<string, unknown>;

function numberValue(name: string, value: unknown, options: {positive?: boolean; nonnegative?: boolean} = {}): number {
  if (typeof value !== "number" || !Number.isFinite(value)) throw new TypeError(`${name} must be a finite number`);
  if (options.positive && value <= 0) throw new RangeError(`${name} must be greater than zero`);
  if (options.nonnegative && value < 0) throw new RangeError(`${name} must be nonnegative`);
  return value;
}

function record(name: string, value: unknown): Row {
  if (!value || typeof value !== "object" || Array.isArray(value)) throw new TypeError(`${name} must be an object`);
  return value as Row;
}

function rows(name: string, value: unknown, minimum = 3): Row[] {
  if (!Array.isArray(value) || value.length < minimum) throw new RangeError(`${name} must contain at least ${minimum} rows`);
  const seen = new Set<string>();
  return value.map((raw, index) => {
    const item = record(`${name}[${index}]`, raw);
    if (typeof item.id !== "string" || !item.id.trim()) throw new RangeError(`${name}[${index}].id must be a nonempty string`);
    if (seen.has(item.id)) throw new RangeError(`${name} ids must be unique`);
    seen.add(item.id);
    return item;
  });
}

function median(values: number[]): number {
  const ordered = [...values].sort((a, b) => a - b);
  const middle = Math.floor(ordered.length / 2);
  return ordered.length % 2 ? ordered[middle] : (ordered[middle - 1] + ordered[middle]) / 2;
}

function summary(values: number[]): Record<string, number> {
  const ordered = [...values].sort((a, b) => a - b);
  return {minimum: ordered[0], median: median(ordered), maximum: ordered.at(-1)!, range: ordered.at(-1)! - ordered[0]};
}

function premiumDiscount(implied: number | null, current: unknown, label = "target.current_price"): number | null {
  if (implied === null || current === undefined || current === null) return null;
  return implied / numberValue(label, current, {positive: true}) - 1;
}

function peComparable(inputs: Row): Row {
  const target = record("target", inputs.target);
  const targetEps = numberValue("target.earnings_per_share", target.earnings_per_share, {positive: true});
  const peerMultiples = rows("peers", inputs.peers).map((peer, index) => {
    const price = numberValue(`peers[${index}].price`, peer.price, {positive: true});
    const eps = numberValue(`peers[${index}].earnings_per_share`, peer.earnings_per_share, {positive: true});
    return {id: peer.id, price, earnings_per_share: eps, pe_ratio: price / eps};
  });
  const multipleSummary = summary(peerMultiples.map(row => row.pe_ratio));
  const selected = multipleSummary.median;
  const implied = selected * targetEps;
  return {model: "median-positive-eps-peer-pe", peer_count: peerMultiples.length, peer_multiples: peerMultiples,
    multiple_summary: multipleSummary, selected_multiple: selected, target_earnings_per_share: targetEps,
    implied_price: implied, premium_discount_to_current: premiumDiscount(implied, target.current_price), state: "valuation-complete"};
}

function evEbitda(inputs: Row): Row {
  const target = record("target", inputs.target);
  const ebitda = numberValue("target.ebitda", target.ebitda, {positive: true});
  const shares = numberValue("target.shares_outstanding", target.shares_outstanding, {positive: true});
  const netDebt = numberValue("target.net_debt", target.net_debt ?? 0);
  const preferred = numberValue("target.preferred_equity", target.preferred_equity ?? 0, {nonnegative: true});
  const nci = numberValue("target.noncontrolling_interest", target.noncontrolling_interest ?? 0, {nonnegative: true});
  const nonoperating = numberValue("target.nonoperating_assets", target.nonoperating_assets ?? 0, {nonnegative: true});
  const peerMultiples = rows("peers", inputs.peers).map((peer, index) => {
    const enterpriseValue = numberValue(`peers[${index}].enterprise_value`, peer.enterprise_value, {positive: true});
    const peerEbitda = numberValue(`peers[${index}].ebitda`, peer.ebitda, {positive: true});
    return {id: peer.id, enterprise_value: enterpriseValue, ebitda: peerEbitda, ev_ebitda: enterpriseValue / peerEbitda};
  });
  const multipleSummary = summary(peerMultiples.map(row => row.ev_ebitda));
  const selected = multipleSummary.median;
  const impliedEnterprise = selected * ebitda;
  const impliedEquity = impliedEnterprise - netDebt - preferred - nci + nonoperating;
  const impliedPrice = impliedEquity > 0 ? impliedEquity / shares : null;
  return {model: "median-positive-ebitda-peer-ev-ebitda", peer_count: peerMultiples.length, peer_multiples: peerMultiples,
    multiple_summary: multipleSummary, selected_multiple: selected, target_ebitda: ebitda,
    implied_enterprise_value: impliedEnterprise, equity_bridge: {net_debt: netDebt, preferred_equity: preferred,
      noncontrolling_interest: nci, nonoperating_assets: nonoperating}, implied_equity_value: impliedEquity,
    shares_outstanding: shares, implied_price: impliedPrice,
    premium_discount_to_current: premiumDiscount(impliedPrice, target.current_price),
    state: impliedPrice === null ? "nonpositive-equity-bridge" : "valuation-complete"};
}

function priceToBook(inputs: Row): Row {
  const target = record("target", inputs.target);
  const targetBvps = numberValue("target.book_value_per_share", target.book_value_per_share, {positive: true});
  const peerMultiples = rows("peers", inputs.peers).map((peer, index) => {
    const price = numberValue(`peers[${index}].price`, peer.price, {positive: true});
    const bvps = numberValue(`peers[${index}].book_value_per_share`, peer.book_value_per_share, {positive: true});
    return {id: peer.id, price, book_value_per_share: bvps, price_to_book: price / bvps};
  });
  const multipleSummary = summary(peerMultiples.map(row => row.price_to_book));
  const selected = multipleSummary.median;
  const implied = selected * targetBvps;
  return {model: "median-positive-book-value-peer-pb", peer_count: peerMultiples.length, peer_multiples: peerMultiples,
    multiple_summary: multipleSummary, selected_multiple: selected, target_book_value_per_share: targetBvps,
    implied_price: implied, premium_discount_to_current: premiumDiscount(implied, target.current_price), state: "valuation-complete"};
}

function peg(inputs: Row): Row {
  const target = record("target", inputs.target);
  const forwardPe = numberValue("target.forward_pe", target.forward_pe, {positive: true});
  const growth = numberValue("target.expected_eps_growth_percent", target.expected_eps_growth_percent, {positive: true});
  const peerRatios = rows("peers", inputs.peers).map((peer, index) => {
    const peerPe = numberValue(`peers[${index}].forward_pe`, peer.forward_pe, {positive: true});
    const peerGrowth = numberValue(`peers[${index}].expected_eps_growth_percent`, peer.expected_eps_growth_percent, {positive: true});
    return {id: peer.id, forward_pe: peerPe, expected_eps_growth_percent: peerGrowth, peg_ratio: peerPe / peerGrowth};
  });
  const pegSummary = summary(peerRatios.map(row => row.peg_ratio));
  const targetPeg = forwardPe / growth;
  const impliedPe = pegSummary.median * growth;
  const forwardEps = target.forward_earnings_per_share === undefined || target.forward_earnings_per_share === null
    ? null : numberValue("target.forward_earnings_per_share", target.forward_earnings_per_share, {positive: true});
  const impliedPrice = forwardEps === null ? null : impliedPe * forwardEps;
  return {model: "forward-pe-divided-by-growth-percentage-points", growth_unit: "percentage-points",
    peer_count: peerRatios.length, peer_ratios: peerRatios, peg_summary: pegSummary, target_forward_pe: forwardPe,
    target_growth_percent: growth, target_peg_ratio: targetPeg, selected_peer_peg: pegSummary.median,
    relative_peg: targetPeg / pegSummary.median, implied_forward_pe: impliedPe,
    forward_earnings_per_share: forwardEps, implied_price: impliedPrice,
    premium_discount_to_current: premiumDiscount(impliedPrice, target.current_price),
    state: impliedPrice === null ? "ratio-only" : "valuation-complete"};
}

function solve(matrix: number[][], vector: number[]): number[] {
  const n = vector.length;
  const augmented = matrix.map((row, index) => [...row, vector[index]]);
  for (let column = 0; column < n; column += 1) {
    let pivot = column;
    for (let row = column + 1; row < n; row += 1) if (Math.abs(augmented[row][column]) > Math.abs(augmented[pivot][column])) pivot = row;
    if (Math.abs(augmented[pivot][column]) <= 1e-12) throw new RangeError("regression design matrix is rank deficient");
    [augmented[column], augmented[pivot]] = [augmented[pivot], augmented[column]];
    const scale = augmented[column][column];
    augmented[column] = augmented[column].map(value => value / scale);
    for (let row = 0; row < n; row += 1) {
      if (row === column) continue;
      const factor = augmented[row][column];
      augmented[row] = augmented[row].map((value, index) => value - factor * augmented[column][index]);
    }
  }
  return augmented.map(row => row.at(-1)!);
}

function features(name: string, row: Row): number[] {
  return [1, numberValue(`${name}.expected_growth_percent`, row.expected_growth_percent) / 100,
    numberValue(`${name}.return_on_equity_percent`, row.return_on_equity_percent) / 100,
    numberValue(`${name}.net_debt_to_ebitda`, row.net_debt_to_ebitda)];
}

function regression(inputs: Row): Row {
  const peers = rows("peers", inputs.peers, 6);
  const target = record("target", inputs.target);
  const xRows: number[][] = [];
  const y: number[] = [];
  const multiples: number[] = [];
  peers.forEach((peer, index) => {
    const multiple = numberValue(`peers[${index}].multiple`, peer.multiple, {positive: true});
    xRows.push(features(`peers[${index}]`, peer)); y.push(Math.log(multiple)); multiples.push(multiple);
  });
  const width = xRows[0].length;
  const xtx = Array.from({length: width}, (_, i) => Array.from({length: width}, (_, j) => xRows.reduce((sum, row) => sum + row[i] * row[j], 0)));
  const xty = Array.from({length: width}, (_, i) => xRows.reduce((sum, row, index) => sum + row[i] * y[index], 0));
  const beta = solve(xtx, xty);
  const fittedLogs = xRows.map(row => row.reduce((sum, value, index) => sum + value * beta[index], 0));
  const mean = y.reduce((a, b) => a + b, 0) / y.length;
  const sse = y.reduce((sum, value, index) => sum + (value - fittedLogs[index]) ** 2, 0);
  const sst = y.reduce((sum, value) => sum + (value - mean) ** 2, 0);
  const rSquared = sst === 0 ? (sse === 0 ? 1 : 0) : 1 - sse / sst;
  const fittedPeers = peers.map((peer, index) => ({id: peer.id, observed_multiple: multiples[index],
    fitted_multiple: Math.exp(fittedLogs[index]), log_residual: y[index] - fittedLogs[index]}));
  const targetX = features("target", target);
  const predictedLog = targetX.reduce((sum, value, index) => sum + value * beta[index], 0);
  const impliedMultiple = Math.exp(predictedLog);
  const metric = numberValue("target.valuation_metric", target.valuation_metric, {positive: true});
  const impliedValue = impliedMultiple * metric;
  return {model: "ols-log-multiple-on-growth-roe-and-leverage", peer_count: peers.length,
    feature_order: ["intercept", "expected_growth_decimal", "return_on_equity_decimal", "net_debt_to_ebitda"],
    coefficients: {intercept: beta[0], expected_growth_decimal: beta[1], return_on_equity_decimal: beta[2], net_debt_to_ebitda: beta[3]},
    r_squared_log_space: rSquared, fitted_peers: fittedPeers, target_predicted_log_multiple: predictedLog,
    implied_multiple: impliedMultiple, target_valuation_metric: metric, implied_value: impliedValue,
    premium_discount_to_current: premiumDiscount(impliedValue, target.current_value, "target.current_value"),
    smearing_correction: "not-applied", state: "valuation-complete"};
}

export function calculate(topicId: string, rawInputs: unknown): Row {
  const inputs = record("inputs", rawInputs);
  if (topicId === "D18-F03-A01") return peComparable(inputs);
  if (topicId === "D18-F03-A02") return evEbitda(inputs);
  if (topicId === "D18-F03-A03") return priceToBook(inputs);
  if (topicId === "D18-F03-A04") return peg(inputs);
  if (topicId === "D18-F03-A05") return regression(inputs);
  throw new RangeError(`unsupported topic_id: ${topicId}`);
}
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