如何按年份及首数字（月份标识）排序文件名字符向量？

Great question! Let's break down why these two functions gave identical output in your case, and clarify their underlying sorting logic.

Core Difference Between sort() and mixedsort() #

• sort() (base R)：Uses lexicographical (dictionary) order by default. It compares strings character-by-character from left to right, following your system's locale or ASCII rules for character priority.
• mixedsort() (gtools package)：Performs "natural sorting"—it splits strings into numeric and non-numeric segments, sorts numeric parts by their actual numeric value, and non-numeric parts lexicographically. This aligns better with how humans intuitively sort strings containing numbers.

Why They Produced Identical Results for Your Vector #

Your filename vector follows a consistent structure: [numeric prefix] [month text] [year].txt. In this specific scenario, the lexicographical sorting of sort() happened to perfectly match the natural sorting of mixedsort():

1. Numeric prefix grouping
   Both functions group items by their leading number (1, 2, 3). For sort(), the character values '1' < '2' < '3' (per ASCII/locale rules) drive this grouping. For mixedsort(), the numeric values 1 < 2 < 3 do the same. The result here is identical.

2. Within same-prefix subgroups
   Let’s break down each group:

   • Prefix 1: "1 Janu 1998.txt" vs "1 Jan 1999.txt"
     • mixedsort() recognizes the year numbers (1998 < 1999) and places the 1998 file first.
     • sort() compares characters left-to-right: the 6th character of "1 Janu..." is 'u', while "1 Jan..." has a space here. In your system’s locale, spaces are ordered after letters, so "1 Janu..." comes first—coincidentally matching the year-based order.
   • Prefix 2: "2 February 1998.txt" vs "2 Feb. 1999.txt"
     • mixedsort() prioritizes the earlier year (1998) first.
     • sort() compares the 6th character: "February" has 'r', while "Feb." has '.'. In your locale, '.' is ordered after 'r', so "February..." comes first—again matching the year-based order.
   • Prefix 3: "3 Marc 1999.txt" vs "3 March. 1998.txt"
     • mixedsort() places the 1999 file first (1999 > 1998).
     • sort() compares the 7th character: "Marc" has a space, while "March" has 'h'. Spaces are ordered after 'h' in your locale, so "Marc..." comes first—aligning with the year order.

Is Your Sorting Logic Correct? #

If your goal is to sort by the numeric value of the leading prefix (e.g., ensuring 2 comes before 10, not the other way around) and numeric year, then mixedsort() is the reliable choice. While sort() worked here by coincidence, it would fail with multi-digit prefixes. For example, "10 Oct 2000.txt" would be sorted before "2 Feb 1999.txt" by sort(), but mixedsort() would place "2 Feb..." first, which is logically correct.

内容的提问来源于stack exchange，提问作者Citizen