Mastering Array Selection and Indexing in Data Processing

Unlock the power of array selection and indexing techniques through a series of educational slides. Explore different methods for selecting elements from arrays and dive into various indexing strategies, suitable for beginners and experienced professionals alike. Gain insights into cell structures, subarrays, and major elements within 3D arrays, along with practical examples showcasing efficient indexing practices in data manipulation.

• Array selection
• Indexing
• Data processing
• 3D arrays
• Beginners

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1. 1 Selecting from Arrays Richard Park (16/04/2020)

2. 2 What? Indexing? Pfffft

3. 3 Selecting from Arrays: Audience Mainly beginners Experienced APLers also

4. 4 Simple Choose Reach The rank operator Sane Select Choose Cells

5. 5 Simple Choose Reach Indexed assignment A 'YEAST' A[3 4] 'E' Modified assignment A 1 9 A[1]+ 5 Optimised

6. 8 Cells, subarrays and elements 3D Array Major cell: Matrix Dimensions / Axes A 2 3 4 A A 2 3 4 A A 2 3 4 A A 2 3 4 A A 2 3 4 A M N O P A A B B C C D D Q R S T E E F F G G H H U V W X I I J J K K L L

7. 9 Cells, subarrays and elements 3D Array Major cell: Matrix 1-cell:Vector A 2 3 4 A M N O P A B C D Q R S T E F G H U V W X I J K L

8. 10 Cells, subarrays and elements 3D Array Major cell: Matrix 1-cell:Vector 0-cell: Scalar A 2 3 4 A M N O P A B C D Q R S T E F G H U V W X I J K L

9. 11 Simple indexing A 2 3 4 A A[1;;] ABCD EFGH IJKL A B C D E F G H I J K L

10. 12 Simple indexing A 2 3 4 A 1 A ABCD EFGH IJKL A B C D E F G H I J K L

11. 13 Simple indexing A 2 3 4 A A[1;2;] EFGH E F G H

12. 14 Simple indexing A 2 3 4 A 1 2 A EFGH E F G H

13. 15 Simple indexing A 2 3 4 A A[1;2;3] G G

14. 16 Simple indexing A 2 3 4 A 1 2 3 A G G

15. 19 Simple indexing A 2 3 4 A A[1 2;2 3;3 4] (1 2)(2 3)(3 4) A GH KL ST WX M N O P A B C D Q R S T E F G H U V W X I J K L

16. 20 Simple indexing A 2 3 4 A A[1 2;1 3;1 4] (1 2)(1 3)(1 4) A AD IL MP UX M N O P A B C D Q R S T E F G H U V W X I J K L

17. 21 Simple indexing A 2 3 4 A ABCD EFGH IJKL MNOP QRST UVWX A[1 2;1 3;1 4] (1 2)(1 3)(1 4) A AD IL MP UX

18. 25 Choose indexing A 2 3 4 A ABCD EFGH IJKL MNOP QRST UVWX A[(1 1 1)(2 1 4)(1 3 4)] APL

19. 26 Choose indexing A 2 3 4 A ABCD EFGH IJKL MNOP QRST UVWX A[(1 1 1)(2 1 4)(1 3 4)] APL

20. 27 Reach indexing nest 2 2 2 (2 2 'DYAL') 1 2 3 (2 2 'ABCD') ('AE' 'IO' 'U') 'NT' 4 DY 1 AL 2 3 AB CD AE IO U NT 4

21. 28 Reach indexing nest[ 2 1 2] AE IO U 2 1 2 2 1 2 nest DY 1 AL 2 3 AB CD AE IO U NT 4

22. 29 Reach indexing nest[ (2 1 2)2] IO (2 1 2)2 2 1 2 2 nest DY 1 AL 2 3 AB CD AE IO U NT 4

23. 30 Reach indexing nest[ (2 1 2)2(2)] nest DY 1 AL 2 3 AB CD AE IO U NT 4 O (2 1 2)2(2) 2 1 2 2 2

24. 31 Reach indexing nest DY 1 AL 2 3 AB CD AE IO U NT 4 DOMAIN ERROR ( (2 1 2)2(2)) nest (2 1 2)2(2) 2 1 2 2 2

25. 32 Pick Reach indexing ((2 1 2))2(2) nest nest DY 1 AL 2 3 AB CD AE IO U NT 4 O (2 1 2)2(2) 2 1 2 2 2

26. 33 Pick Reach indexing 'this' 'that' 'the other thing' this that theother thing 3 'this' 'that' 'the other thing' the other thing

27. 34 Simple Subarrays Choose 0-cells AKA Scalars Reach Nested arrays

28. 35 Squad Indexing as a function you can use operators A 2 3 4 A ABCD EFGH IJKL MNOP QRST UVWX 2 2 A 2 [2]A EFGH QRST

29. 37 Squad with axis [] A 2 3 4 A 2 [1]A MNOP QRST UVWX M N O P A B C D Q R S T E F G H U V W X I J K L

30. 38 Squad with rank A 2 3 4 A 2 3 A MNOP QRST UVWX M N O P A B C D Q R S T E F G H U V W X I J K L

31. 39 Squad with axis [] A 2 3 4 A 2 [2]A EFGH QRST M N O P A B C D Q R S T E F G H U V W X I J K L

32. 40 Squad with rank A 2 3 4 A 2 2 A EFGH QRST M N O P A B C D Q R S T E F G H U V W X I J K L

33. 41 Squad with rank A 2 3 4 A 2 2 A EFGH QRST M N O P A B C D Q R S T E F G H U V W X I J K L

34. 42 Squad with axis [] A 2 3 4 A 2 [3]A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

35. 43 Squad with rank A 2 3 4 A 2 1 A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

36. 44 Squad with rank A 2 3 4 A 2 1 A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

37. 45 Squad with rank A 2 3 4 A 2 1 A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

38. 46 Squad with rank A 2 3 4 A 2 1 A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

39. 47 Squad with rank A 2 3 4 A 2 1 A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

40. 48 Squad with rank A 2 3 4 A 2 1 A BFJ NRV M N O P A B C D Q R S T E F G H U V W X I J K L

41. 51 Squad with rank n 3 5 15 1 3 4 0 2 n 1 6 11 2 7 12 3 8 13 4 9 14 5 10 15 1 6 11 3 8 13 4 9 14

42. 52 Squad with rank n 3 5 15 1 3 4 0 99 n 1 6 11 2 7 12 3 8 13 4 9 14 5 10 15 1 6 11 3 8 13 4 9 14

43. 53 "Sane" indexing I 0 99 n 3 5 15 ( 1 3 4) n "Insane" 1 6 11 3 8 13 4 9 14 1 6 11 2 7 12 3 8 13 4 9 14 5 10 15 1 3 4 I n 1 6 11 3 8 13 4 9 14

44. 54 "Sane" indexing I 0 99 n 3 5 15 1 3 4 I n 1 6 11 3 8 13 4 9 14 1 0 1 1 0 n 1 6 11 3 8 13 4 9 14 1 6 11 2 7 12 3 8 13 4 9 14 5 10 15

45. 55 "Sane" indexing 'APPLE'[1 3 4] Intuitive, beginner friendly APL 1 0 1 1 0/'APPLE' Booleans APL

46. 56 "Sane" indexing 1 3 4 I 'APPLE' Sane APL 1 0 1 1 0 'APPLE' Rank polymorphic APL

47. 57 The Indexer AKA Select I (( ) ) 0 99

48. 58 The Indexer AKA Select I (( ) ) 0 99 1 I A 1 A A[1;;] 1 0 99 A ABCD EFGH IJKL

49. 59 The Indexer AKA Select I (( ) ) 0 99 A 2 3 4 A ABCD EFGH IJKL MNOP QRST UVWX (1 2)(2 3) I A EFGH UVWX A[(1 2, 2 3) ., 4] EFGH UVWX

50. 60 The Indexer AKA Select I (( ) ) 0 99 A 2 3 4 A ABCD EFGH IJKL MNOP QRST UVWX (1 2 4)(2 3) I A H UVWX

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