dayan-numerology.md

Dayan Numerology / 大衍之数

The Dayan Numerology system is the core framework for analyzing stroke count fortune in name studies, mapping numbers 1-81 to different fortune attributes and detailed interpretations.

81 Numerology Concepts

The I Ching · Great Commentary states: "The numbers of the Great Expansion amount to fifty, of which forty-nine are used." In this project, the Dayan Numbers are extended into a 1-81 stroke count fortune system, used for name stroke analysis.

Each number contains the following dimensions:

Dimension	Field	Description
Stroke Count	Number	1-81
Fortune	JiXiong	Auspicious/Inauspicious/Semi-Auspicious
Female Fortune	NvMing	Female-specific fortune (empty means gender-neutral)
Most Auspicious	IsMax	Whether it's the most auspicious number
Corresponding Hexagram	Gua	Corresponding hexagram name
Tian Jiu	TianJiu	Taiji number name
Imagery	YiXiang	Imagery description
Foundation	Foundation	Career foundation
Family	Family	Family situation
Health	Health	Health tips
Meaning	Meaning	Detailed meaning interpretation

Dayan Struct

type Dayan struct {
    Number     int    // Stroke count (1-81)
    JiXiong    string // Fortune (吉/凶/半吉)
    NvMing     string // Female-specific fortune
    IsMax      bool   // Whether most auspicious
    Gua        string // Corresponding hexagram
    TianJiu    string // Tian Jiu (Taiji number)
    YiXiang    string // Imagery
    Foundation string // Foundation
    Family     string // Family
    Health     string // Health
    Meaning    string // Meaning
}

API

Querying Numerology

// Query by stroke count (1-81)
dayan, err := yi.GetDayan(21)
if err != nil {
    // err == ErrInvalidDayanNumber (out of 1-81 range)
    panic(err)
}
fmt.Printf("Stroke: %d\n", dayan.Number)
fmt.Printf("Fortune: %s\n", dayan.JiXiong)
fmt.Printf("Tian Jiu: %s\n", dayan.TianJiu)
fmt.Printf("Imagery: %s\n", dayan.YiXiang)
fmt.Printf("Foundation: %s\n", dayan.Foundation)
fmt.Printf("Family: %s\n", dayan.Family)
fmt.Printf("Health: %s\n", dayan.Health)
fmt.Printf("Meaning: %s\n", dayan.Meaning)

// Ignore errors (out of bounds returns zero value)
dayan2 := yi.MustGetDayan(100) // returns Dayan{}

Fortune Judgment

dayan, _ := yi.GetDayan(21)

// Is auspicious (吉 or 半吉)
fmt.Printf("Is auspicious: %v\n", dayan.IsJi())

// Is inauspicious
fmt.Printf("Is inauspicious: %v\n", dayan.IsXiong())

// Suitable for female
fmt.Printf("Suitable for female: %v\n", dayan.IsSuitableForFemale())

// Is most auspicious
fmt.Printf("Most auspicious: %v\n", dayan.IsBest())

Application Scenarios

Name Stroke Fortune Analysis

The most common application of Dayan Numbers is name stroke analysis. Take the total stroke count of a name modulo 81 (treating 0 as 81), then query the corresponding fortune:

package main

import (
    "fmt"
    "github.com/godcong/yi"
)

func analyzeStroke(strokeCount int) {
    // Modulo 81
    n := strokeCount % 81
    if n == 0 {
        n = 81
    }

    dayan, err := yi.GetDayan(n)
    if err != nil {
        fmt.Printf("Invalid stroke count: %d\n", n)
        return
    }

    fmt.Printf("Stroke count %d (original %d):\n", n, strokeCount)
    fmt.Printf("  Fortune: %s\n", dayan.JiXiong)
    fmt.Printf("  Imagery: %s\n", dayan.YiXiang)
    fmt.Printf("  Foundation: %s\n", dayan.Foundation)
    fmt.Printf("  Family: %s\n", dayan.Family)
    fmt.Printf("  Health: %s\n", dayan.Health)
    fmt.Printf("  Meaning: %s\n", dayan.Meaning)
}

func main() {
    analyzeStroke(21)
    analyzeStroke(34)
    analyzeStroke(81)
}

Combined with Five Elements Analysis

Stroke counts can also be combined with the Five Elements system for richer analysis:

strokeCount := 21
dayan, _ := yi.GetDayan(strokeCount % 81)

// Five Elements corresponding to stroke count
wuxing := yi.GetWuXingByNumber(strokeCount)
fmt.Printf("Element: %s\n", wuxing)  // e.g., "阳木" (Yang Wood)

// Fortune combined with Five Elements
fmt.Printf("Stroke %d: %s, Element %s\n", strokeCount, dayan.JiXiong, wuxing)

Data Notes

⚠️ Known Data Gaps:

• Gua.JiXiong: Some hexagram fortune fields are empty (incomplete source data, not a bug)
• Yao.NvMing: Most line female fortune fields are empty. Empty means gender-neutral, not missing data
• Only Qian and Kun hexagrams have Yong (Yong Jiu / Yong Liu) and YongJiXiong fields

These are source data limitations and do not affect core functionality. IsJi() and IsXiong() methods return false when JiXiong is empty.