| Feature selection | 20 Newsgroups | Reuters-21578 | Industry Sector | TechTC-100 |
| Initial vocabulary | 103,135 | 22,792 | 64,680 | 103,003 | CF ≥ 2 | 63,285 | 13,809 | 38,107 | 55,250 | CF ≥ 5 | 34,152 | 7,268 | 21,681 | 29,070 | CF ≥ 10 | 21,845 | 4,455 | 14,767 | 18,946 | CF ≥ 20 | 13,792 | 2,626 | 9,885 | 12,254 | CF ≥ 50 | 7,166 | 1,224 | 5,722 | 6,593 | CF ≥ 100 | 4,056 | 689 | 3,580 | 3,937 | CF ≥ 200 | 2,091 | 345 | 2,057 | 2,249 | CF ≥ 500 | 693 | 110 | 854 | 936 | CF ≥ 1000 | 230 | 36 | 420 | 432 | CF ≥ 2000 | 57 | 18 | 159 | 195 |
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