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I use the property "pages" for the number of pages of an article or book.

There are two problems.

First:

If I use C-c ^ to sort the items by the value of pages org-sort seems to interpret the numbers lexicographically: 1<100<20<3. Of course I need the natural order of numbers: 1<3<20<100.

Second:

If I use C-c a m to search for items with pages<20 I get the correct items and the "wrong" items: where the pages property is not defined. How to ignore the "wrong" items?

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For the first problem, you have to use a function like this:

#+BEGIN_SRC emacs-lisp
(defun sort-by-pages ()
 (string-to-number (org-entry-get nil "pages")))
#+END_SRC

then type C-c ^ f and select the function sort-by-pages. The problem is properties in org-mode are strings, and you need this to convert them to numbers.

For problem two try: pages<20+pages<>"" the second one should eliminate the nulls.

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  • Thanks, this solves both problems. But for the first one. Can I make the function more general?: With one argument, the name of the numerical property, for example "pages". (I have more than one numerical property. It's not good to define a new function for every new numerical property.) – rl1 Apr 23 '17 at 21:04
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    I don't think you can do that. I am pretty sure no arguments are allowed. – John Kitchin Apr 23 '17 at 22:06
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I also used org properties for page numbers and have trouble sorting them numerically. I added your function, but when I use org-sort-entries, it first ask for Function for extracting keys:, which I select the sort-by-pages function. Then Emacs asks for Function for comparing keys (empty for default 'sort-subr' predicate):, which I don't know what to select here. Sorry if this is a dumb question as I don't know lisp yet. I've tried a couple functions based on intuition such as sort but get Wrong type argument: list-or-vector-p, 6

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  • Have you tried just to type ENTER after (empty for default 'sort-subr' predicate):? – rl1 Apr 8 at 17:01
  • yes, the output is Wrong number of arguments: (1 . 1), 2 – tim Apr 8 at 18:56
  • I don't know. I tested it again, it works. Maybe you should ask your question with details in a new thread. It's unlikely that much people read your question here. – rl1 Apr 8 at 19:52

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