text_hashing_trick.qmd

---
execute:
  freeze: true
---

[R/preprocessing.R](https://github.com/rstudio/keras//blob/main/R/preprocessing.R#L234) 

# text_hashing_trick

## Converts a text to a sequence of indexes in a fixed-size hashing space.

## Description
 Converts a text to a sequence of indexes in a fixed-size hashing space. 


## Usage
```r
 
text_hashing_trick( 
  text, 
  n, 
  hash_function = NULL, 
  filters = "!\"#$%&()*+,-./:;<=>?@[\\]^_`{|}~\t\n", 
  lower = TRUE, 
  split = " " 
) 
```

## Arguments
|Arguments|Description|
|---|---|
| text | Input text (string). |
| n | Dimension of the hashing space. |
| hash_function | if `NULL` uses the Python `hash()` function. Otherwise can be `'md5'` or any function that takes in input a string and returns an int. Note that `hash` is not a stable hashing function, so it is not consistent across different runs, while `'md5'` is a stable hashing function. |
| filters | Sequence of characters to filter out such as punctuation. Default includes basic punctuation, tabs, and newlines. |
| lower | Whether to convert the input to lowercase. |
| split | Sentence split marker (string). |

## Details
 Two or more words may be assigned to the same index, due to possible collisions by the hashing function. 


## Value
 A list of integer word indices (unicity non-guaranteed). 



## See Also
 Other text preprocessing:  `make_sampling_table()`, `pad_sequences()`, `skipgrams()`, `text_one_hot()`, `text_to_word_sequence()`