fintech-algorithms
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Ratios, Proportions, Rates, and Percentages

Install and import#

bash
npm install fintech-algorithms
ts
import { ratiosProportionsRatesAndPercentages } from "fintech-algorithms/foundations/mathematical-language-and-quantitative-reasoning/ratios-proportions-rates-and-percentages";

Signature#

ratiosProportionsRatesAndPercentages(input)

Turns a part-and-whole pair into a ratio and a percentage, and turns the same part spread over an elapsed span into a rate per period.

Parameters#

NameTypeNotes
inputD00InputA plain object. Every F01 topic first reads values, which must be a non-empty array of finite numbers, and validates it before any per-topic branch runs. This topic then reads part, whole and elapsed, each coerced with Number; values is demanded but not used by this calculation.

Returns#

{ ratio: number; percentage: number; ratePerPeriod: number }

ratio is part / whole, percentage is that ratio times 100, and ratePerPeriod is part / elapsed.

Errors#

  • When input is not a plain object — throws TypeError
  • When values is missing, empty, or not an array — throws RangeError
  • When values contains a value that is not a finite number — throws RangeError
  • When whole is zero, or elapsed is zero or negative — throws RangeError

Complexity: time O(n), space O(n).

Worked example#

verified This is the worked example published in the article, replayed by the test suite on every run. The output cannot drift.

Input#

input
{
  "values": [1, 2, 3, 4, 5],
  "startingCash": 1000,
  "inflows": 250,
  "outflows": 120,
  "slope": 2,
  "intercept": 1,
  "part": 25,
  "whole": 200,
  "elapsed": 5,
  "old": 4.5,
  "new": 4.75,
  "base": 16,
  "exponent": 0.5,
  "a": 2
}

Showing 14 of 28 fields.

Call#

ratiosProportionsRatesAndPercentages(input)

Returns#

object with 2 fields: ratio, percentage

{
  "ratio": 0.125,
  "percentage": 12.5
}

Diagrams#

Ratios, Proportions, Rates, and Percentages — concept anatomy
Ratios, Proportions, Rates, and Percentages — lesson map
Ratios, Proportions, Rates, and Percentages — mistake contrast

Calculation flow#

Ratios, Proportions, Rates, and Percentages — four-part map 
flowchart LR
    A["Name the input"] --> B["Apply: expense share = expenses / revenue; cost per customer = expenses / customers"]
    B --> C["Check units and boundary"]
    C --> D["Explain the output"]

How it works#

This page states the contract — how to call it correctly. The article explains the concept: why it works, and where it breaks.

Read the article →

References#

  • NIST/SEMATECH e-Handbook of Statistical Methods — NIST/SEMATECH
  • Author-derived and synthetic boundary

The rest of the Mathematical Language and Quantitative Reasoning family#