Dealing With Higher Rank Arrays

[conor_f]

I am trying to get to grips with arrays of rank > 2. I have read the relevant sections of "Mastering Dyalog APL" and searched the APLwiki, but am still not satisfied. An example I could get a start from would be ideal for me, so if someone could show me a short section of code in which an array of rank ≥ 3 is created and initialised to some values, has items appended and dropped from it and an example of the effects of operators/functions like ¨ , / . etc, I would be very grateful.

Thanks in advance

[Roger|Dyalog]

Ken Iverson (inventor of APL) liked to use the following analogy: numbers, lists, tables, reports, files, drawers, cabinets, aisles, floors, warehouses, ...

Examples:

      ⎕rl←7*5            ⍝ to get reproducible random numbers
      ⎕io←0              ⍝ because I detest 1-origin

      x←?5 4 3⍴100       ⍝ random numbers for testing
                         ⍝ sales in 5 countries, 4 quarters, and 3 months in a quarter

      +/x                ⍝ sales in each country by quarter
      +/[2] x            ⍝ ditto

      +/[0] x            ⍝ sales for each month

      +/[1]+/[2] x       ⍝ sales in each country

      +/[0]+/[1]+/[2] x  ⍝ total sales
      +/,x               ⍝ ditto

[conor_f]

Great, thanks. Just takes a bit to get used to them I suppose.