Re: Any faster way to find frequency of words?

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Jean Louis <bugs@gnu.support> writes:

> I am interested if there is some better way for Emacs Lisp to find
> frequency of words.
>
> Purpose is to create HTML clickable tag clouds similar to image tag
> clouds. But I will invoke Perl from Emacs to generate it. For that, I
> have to analyze the text first.

Is there any particular improvement you're trying to make?

> (setq text "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam
> lectus. Sed sit amet ipsum mauris. Maecenas congue ligula ac quam
> viverra nec consectetur ante hendrerit. Maecenas congue ligula ac quam
> viverra nec consectetur ante hendrerit..")
>
> (defun text-alphabetic-only (text)
>   "Return alphabetic characters from TEXT."
>   (replace-regexp-in-string "[^[:alpha:]]" " " text))
>
> (defun word-frequency (text &optional length)
>   "Returns word frequency as hash from TEXT."
>   (let* ((hash (make-hash-table :test 'equal))
> 	 (text (text-alphabetic-only text))
> 	 (words (split-string text " " t " ")))

I guess I'd suggest using Emacs syntax parsing functions, ie
`forward-word' and `buffer-substring'. Then you can fine tune the
definition of words using the local syntax table.

>     (mapc (lambda (word)
> 	    (when (> (length word) 2)
> 	      (let ((word (downcase word)))
> 		(if (numberp (gethash word hash))
> 		    (puthash word (1+ (gethash word hash)) hash)
> 		  (puthash word 1 hash)))))

While hash tables are probably best for very large texts, alists are
nice because you can use place-setting with a default, simplifying the
above to:

(cl-incf (alist-get word frequency-alist 0 nil #'equal))

Eric