Datasets:
metadata
language:
- ja
license: mit
size_categories:
- 1K<n<10K
task_categories:
- text-classification
tags:
- japanese
- text-difficulty
- language-learning
- linguistics
- aozora-bunko
- educational
- curriculum-design
configs:
- config_name: default
data_files:
- split: train
path: data/train-*
dataset_info:
features:
- name: text
dtype: string
- name: footnote
dtype: string
- name: meta
dtype: string
- name: overall_difficulty
dtype: float64
- name: kanji_difficulty
dtype: float64
- name: lexical_difficulty
dtype: float64
- name: grammar_complexity
dtype: float64
- name: sentence_complexity
dtype: float64
- name: difficulty_level
dtype: string
- name: text_length
dtype: int64
- name: kanji_density
dtype: float64
- name: avg_sentence_length
dtype: float64
- name: joyo_grade_avg
dtype: float64
- name: lexical_diversity
dtype: float64
- name: non_joyo_percentage
dtype: float64
- name: avg_word_length
dtype: float64
- name: katakana_percentage
dtype: float64
- name: word_frequency_score
dtype: float64
- name: sentence_length_variance
dtype: float64
- name: grammar_complexity_score
dtype: float64
- name: difficulty_score
dtype: float64
splits:
- name: train
num_bytes: 182916878
num_examples: 5000
download_size: 94427207
dataset_size: 182916878
Aozora Text Difficulty Dataset
This dataset contains Japanese literary texts from the Aozora Bunko digital library, enhanced with jReadability-based difficulty analysis for Japanese language learning and curriculum development.
Dataset Overview
- Source: Aozora Bunko (青空文庫) - Japan's premier digital library of public domain literature
- Enhancement: jReadability-based difficulty scoring using research-backed Japanese readability models
- Primary Methodology: jReadability - A Python implementation of Lee & Hasebe's Japanese readability evaluation system
- Use Cases: Japanese language curriculum design, reading level assessment, adaptive learning systems, difficulty-controlled text generation
- License: Original Aozora Bunko texts are public domain; analysis code and scores are provided under open source terms
📊 Dataset Structure
Total Records: 5,000 Japanese texts Total Columns: 21 Column Categories: Original Data (3) + Core Difficulty Scores (6) + Detailed Metrics (11) + Legacy Score (1)
🗂️ Column Descriptions
Original Data Columns (3)
| Column | Type | Description |
|---|---|---|
text |
string | Full Japanese text content from Aozora Bunko (50-532,561 characters) |
footnote |
string | Publishing information and bibliographic details in Japanese |
meta |
string | JSON metadata with work ID, title, author, and readings |
Core Difficulty Scores (6) - Main Features for Learning
| Column | Type | Range | Description |
|---|---|---|---|
overall_difficulty |
float64 | 0.0-1.0 | Primary difficulty score based on jReadability model |
kanji_difficulty |
float64 | 0.0-1.0 | Complexity based on kanji grade levels and density |
lexical_difficulty |
float64 | 0.0-1.0 | Vocabulary complexity using authentic frequency data |
grammar_complexity |
float64 | 0.0-1.0 | Grammatical structure complexity |
sentence_complexity |
float64 | 0.0-1.0 | Sentence length and structure variation |
difficulty_level |
string | categorical | Curriculum classification: Beginner/Elementary/Intermediate/Advanced/Expert |
Detailed Linguistic Metrics (11)
| Column | Type | Description |
|---|---|---|
text_length |
int64 | Total character count including punctuation |
kanji_density |
float64 | Proportion of Chinese characters (0.0-1.0) |
avg_sentence_length |
float64 | Average characters per sentence |
joyo_grade_avg |
float64 | Average educational grade of kanji used (1-9 scale) |
lexical_diversity |
float64 | Unique words ÷ total words (vocabulary richness) |
non_joyo_percentage |
float64 | Proportion of advanced kanji beyond standard education |
avg_word_length |
float64 | Average characters per word |
katakana_percentage |
float64 | Proportion of katakana (foreign/technical words) |
word_frequency_score |
float64 | Vocabulary rarity score (0=common, 1=rare) |
sentence_length_variance |
float64 | Statistical variance in sentence lengths |
grammar_complexity_score |
float64 | Grammatical pattern complexity score |
Legacy Compatibility (1)
| Column | Type | Range | Description |
|---|---|---|---|
difficulty_score |
float64 | 0.0-10.0 | Traditional 10-point difficulty scale for compatibility |
🎯 Difficulty Calculation Methodology
Primary Difficulty Score: jReadability Model
The overall_difficulty score is calculated using the jReadability Python library, which implements the research-backed Japanese readability model developed by Jae-ho Lee and Yoichiro Hasebe.
jReadability Model Formula:
readability = {mean words per sentence} × -0.056
+ {percentage of kango} × -0.126 # Chinese-origin words
+ {percentage of wago} × -0.042 # Native Japanese words
+ {percentage of verbs} × -0.145
+ {percentage of particles} × -0.044
+ 11.724
Score Normalization:
- jReadability output: 0.5-6.5 (higher = easier)
- Our normalization:
(6.5 - jreadability_score) / 6.0→ 0-1 scale (higher = harder)
Curriculum Level Classification
- Beginner (0.00-0.19): Basic modern Japanese
- Elementary (0.20-0.34): Simple literary texts
- Intermediate (0.35-0.54): Standard literary works
- Advanced (0.55-0.74): Complex literary language
- Expert (0.75-1.00): Classical or highly sophisticated texts
Supporting Linguistic Metrics
- Kanji Analysis: 3,003 kanji with official educational grades from kanjiapi.dev
- Vocabulary Analysis: wordfreq library with real corpus data
- Grammar Analysis: Pattern-based complexity scoring using formal Japanese constructions
- Sentence Analysis: Length variation and structural complexity measures
Research Foundation
- Lee, J. & Hasebe, Y. Introducing a readability evaluation system for Japanese language education
- Lee, J. & Hasebe, Y. Readability measurement of Japanese texts based on levelled corpora
- Model specifically designed for non-native Japanese learners (not native speaker grade levels)