Let's compute the ARI for a given book. The automated readability index (ARI) is a formula for computing the U.S. grade level for a given block of text. The general formula to compute the ARI is as follows:
The score is computed by multiplying the number of characters divided by the number of words by 4.71, adding the number of words divided by the number of sentences multiplied by 0.5, and subtracting 21.43. If the result is a decimal, always round up, and if the result is higher than 14, it should be set to 14.
Scores correspond to the following ages and grad levels:
Score Ages Grade Level
1 5-6 Kindergarten
2 6-7 First Grade
3 7-8 Second Grade
4 8-9 Third Grade
5 9-10 Fourth Grade
6 10-11 Fifth Grade
7 11-12 Sixth Grade
8 12-13 Seventh Grade
9 13-14 Eighth Grade
10 14-15 Ninth Grade
11 15-16 Tenth Grade
12 16-17 Eleventh grade
13 17-18 Twelfth grade
14 18-22 College
Once you’ve computed the ARI score, you can use the following dictionary to look up the age range and grade level.
ari_scale = {
1: {'ages': '5-6', 'grade_level': 'Kindergarten'},
2: {'ages': '6-7', 'grade_level': '1st Grade'},
3: {'ages': '7-8', 'grade_level': '2nd Grade'},
4: {'ages': '8-9', 'grade_level': '3rd Grade'},
5: {'ages': '9-10', 'grade_level': '4th Grade'},
6: {'ages': '10-11', 'grade_level': '5th Grade'},
7: {'ages': '11-12', 'grade_level': '6th Grade'},
8: {'ages': '12-13', 'grade_level': '7th Grade'},
9: {'ages': '13-14', 'grade_level': '8th Grade'},
10: {'ages': '14-15', 'grade_level': '9th Grade'},
11: {'ages': '15-16', 'grade_level': '10th Grade'},
12: {'ages': '16-17', 'grade_level': '11th Grade'},
13: {'ages': '17-18', 'grade_level': '12th Grade'},
14: {'ages': '18-22', 'grade_level': 'College'}
}The output should look something like the following:
--------------------------------------------------------
The ARI for gettysburg-address.txt is 12
This corresponds to a 11th Grade level of difficulty
that is suitable for an average person 16-17 years old.
--------------------------------------------------------