---
dataset_info:
  features:
  - name: text
    dtype: string
  - name: lang
    dtype: string
  - name: name
    dtype: string
  - name: category
    dtype: string
  - name: year
    dtype: int64
  splits:
  - name: train
    num_bytes: 412136435
    num_examples: 878
  download_size: 209656175
  dataset_size: 412136435
configs:
- config_name: default
  data_files:
  - split: train
    path: data/train-*
language:
- chm
- mhr
- mrj
license: cc-by-4.0
---

# Mari Press and School Books Corpus

## Description
This is a text corpus of [Meadow Mari](https://en.wikipedia.org/wiki/Meadow_Mari_language)
and [Hill Mari](https://en.wikipedia.org/wiki/Hill_Mari_language) languages.
The dataset is plain text without any additional annotations except for basic meta data.
Please note, that the texts have been extracted from PDFs, so they are quite dirty.

## Source
The corpus is based on texts from [Mari Lab](https://mari-lab.ru/index.php/Mari-Lab) PDFs
of magazines and school books.

## Composition

The first part of the corpus includes the following magazines:


| name             | names_in_corpus  | years     | languages                                               |
| ---------------- | ---------------- | --------- | ------------------------------------------------------- |
| У вий            | U_Viy_*          | 1926–1936 | **Meadow Mari** with _rare_ presence of Hill Mari       |
| Пиалан илыш      | пиалан_илыш_*    | 1926–1936 | **Meadow Mari**                                         |
| Родина верч      | родина_верч_*    | 1942–1945 | **Meadow Mari**                                         |
| Марий альманах   | марий_альманах_\*| 1946–1949 | **Meadow Mari**                                         |
| Ончыко           | ончыко_*         | 1954-2022 | **Meadow Mari** with _occasional_ presence of Hill Mari |
| Марий сандылак   | марий_сандалык_* | 2008-2018 | **Meadow Mari** with _occasional_ presence of Hill Mari |
| У сэм            | у_сэм_*          | 1930-1934 | **Hill Mari**                                           |
| Йакшар знамӹ     | йакшар_знамӹ_*   | 1935-1936 | **Hill Mari**                                           |
| У сем            | у_сем_*          | 1990-2018 | **Hill Mari**                                           |

Note 1: _У вий_, _Пиалан илыш_, _Родина верч_, _Марий альманах_ and _Ончыко_ are names of the same magazine
in different years.

Note 2: writing system had minor changes in 1938, if only modern writing is needed, filter by `year` field.

The second part includes school books on geography, mathematics and other subjects from
between 1933-1951.


## Preprocessing

Due to the fact that those are PDFs, a huge amount of preprocessing has been done to convert them to PDFs.
At the beggining the texts have been split into four categories:
* `clean`: clean PDFs that have a text layer in UTF-8
* `ocr`: OCR PDFs have an automatically recognized text layer in UTF-8
* `fix`: broken encoding PDFs that have inconsistent ASCII encoding
* `remap`: slightly broken PDFs that have a text layer in UTF-8 but some charachters are incorrect

PDFs from first and second categories have been used as-is.
PDFs from the third categories have been assumed to be in `cp1251` and converted to UTF-8.
For the third and fourth categories, the incorrect symbols have been remapped to the correct ones.


## Filtering

Sometimes Mari magazines contain sections in Russian language. I have
[trained](https://github.com/OneAdder/mari-llm/blob/master/mari_vs_russian_classifier.py)
a logistic regression classifier on [Meadow-Mari-Russian parallel corpus](https://huggingface.co/datasets/AigizK/mari-russian-parallel-corpora).
It yields zero if a sentence is in Mari and 1 if in Russian. Then I classified each line in sections of PDF texts (separated be two line breaks)
and calculated mean score for each section. Sections that are definitely Russian (>0.8) have been removed.

## Metrics



|          | Total      | Hill Mari only | Meadow Mari only | No OCR    | Modern Writing |
| -------- | ---------- | -------------- | ---------------- | --------- | -------------- |
| texts    | 878        | 176            | 563              | 166       | 701            |
| tokens*  | 45 576 320 | 5 081 705      | 32 426 529       | 8 192 294 | 41 520 480     |

_\*nltk.tokenize.casual.TweetTokenizer not very reliable as there is a lot of rubbish from PDF_

## Cite

```bibtex
@online{mari_press_and_school_books_corpus,
  author = {Andrei Chemyshev and Michael Voronov},
  title = {Mari Press and School Books Corpus},
  year = 2025,
  url = {https://huggingface.co/datasets/OneAdder/mari-pdf-corpus},
  urldate = {2025-07-17}
}
```