Mirror and rotate

[dicom]

Hello

NArray is a wonderful tool in Ruby. However, one thing that I miss with it is a convenient way of rotating or mirroring an array. It might be that I have missed something in the documentation of course, but as far as I can see, there's no (super-easy) way of doing it. I guess I would like to have convenient NArray#rotate and NArray#mirror methods. Then you could do something like this:

---

Proposed method 1:
NArray#mirror(dim=0)
This would be principal method (it would work just fine on arrays of any dimension).

a = NArray.int(3,3).indgen!
=> NArray.int(3,3):
[ [ 0, 1, 2 ],
  [ 3, 4, 5 ],
  [ 6, 7, 8 ] ]

a.mirror
=> NArray.int(3,3):
[ [ 2, 1, 0 ],
  [ 5, 4, 3 ],
  [ 8, 7, 6 ] ]

a.mirror(1)
=> NArray.int(3,3):
[ [ 6, 7, 8 ],
  [ 3, 4, 5 ],
  [ 0, 1, 2 ] ]

---

Proposed method 2:
NArray#rotate(steps)
This would be harder to make principal (it's primarily wanted for two dimensional arrays ('images'), and gets more complicated with vectors or multi-dimensional arrays)

a = NArray.int(3,3).indgen!
=> NArray.int(3,3):
[ [ 0, 1, 2 ],
  [ 3, 4, 5 ],
  [ 6, 7, 8 ] ]

a.rotate(1)
=> NArray.int(3,3):
[ [ 6, 3, 0 ],
  [ 7, 4, 1 ],
  [ 8, 5, 2 ] ]

a.rotate(-1)
=> NArray.int(3,3):
[ [ 2, 5, 8 ],
  [ 1, 4, 7 ],
  [ 0, 3, 6 ] ]

NArray.int(3).indgen!.rotate(1)
=> exception?!

NArray.int(3,3,3).indgen!.rotate(1)
=> exception?!

---

Thanks for your consideration.

Regards,
Chris

[masa16]

I wrote it as new "reverse" and "rot90" methods.
dae4028#lib/narray_ext.rb

"reverse" is named after Array#reverse, "rot90" is named after Numpy method

$a = NArray.int(3,3).indgen!   
#=> NArray.int(3,3): 
[ [ 0, 1, 2 ], 
  [ 3, 4, 5 ], 
  [ 6, 7, 8 ] ]
$a.reverse                     
#=> NArray.int(3,3): 
[ [ 8, 7, 6 ], 
  [ 5, 4, 3 ], 
  [ 2, 1, 0 ] ]
$a.reverse(0)                  
#=> NArray.int(3,3): 
[ [ 2, 1, 0 ], 
  [ 5, 4, 3 ], 
  [ 8, 7, 6 ] ]
$a.reverse(1)                  
#=> NArray.int(3,3): 
[ [ 6, 7, 8 ], 
  [ 3, 4, 5 ], 
  [ 0, 1, 2 ] ]
$a.rot90                       
#=> NArray.int(3,3): 
[ [ 6, 3, 0 ], 
  [ 7, 4, 1 ], 
  [ 8, 5, 2 ] ]
$a.rot90(2)                    
#=> NArray.int(3,3): 
[ [ 8, 7, 6 ], 
  [ 5, 4, 3 ], 
  [ 2, 1, 0 ] ]
$a.rot90(-1)                   
#=> NArray.int(3,3): 
[ [ 2, 5, 8 ], 
  [ 1, 4, 7 ], 
  [ 0, 3, 6 ] ]

[dicom]

Thank you Masahiro,
that was extremely responsive!

One minor comment:
In your commit, for the exception in #rot90, you have:

raise "must be >2 dimensional array"

I believe it should be:

raise "must be >=2 dimensional array"

[dicom]

Closing this issue. Thanks for the implementation.

By the way, it would be nice if you could push the updated documentation file to:
http://narray.rubyforge.org/SPEC.en