NArray shuffle

Ruby
1

Has anyone ever needed to “shuffle” an NArray? I can certainly convert
it to an array and do the sort_by {rand} idiom, and then convert it
back. I currently:

na.size.times do
p1,p2 = rand(na.size),rand(na.size)
na[p1],na[p2] = na[p2],na[p1]
end

which works, but I wondering if anyone knew a better way.
Thanks
pth

2

On Thu, 7 Sep 2006, Patrick H. wrote:

Thanks
pth

if your na is not huge you might use:

 harp:~ > cat a.rb
 require 'narray'

 na = NArray.int(3,2).indgen!

 p na

 idx = NArray.to_na Array.new(na.size){|i| i}.sort_by{ rand }

 na[] = na[idx].reshape *na.shape

 p na


 harp:~ > ruby a.rb
 NArray.int(3,2):
 [ [ 0, 1, 2 ],
   [ 3, 4, 5 ] ]
 NArray.int(3,2):
 [ [ 0, 3, 1 ],
   [ 2, 4, 5 ] ]

which at least does it in one hit at the cost of space.

-a

3

“Patrick H.” [email protected] writes:

Has anyone ever needed to “shuffle” an NArray? I can certainly convert
it to an array and do the sort_by {rand} idiom, and then convert it
back. I currently:

What about:

shuffled = orig[NArray.float(*orig.shape).random!.sort_index]

4

On 9/6/06, Daniel M. [email protected] wrote:

–
s=%q( Daniel M. – [email protected]
puts “s=%q(#{s})”,s.map{|i|i}[1] )
puts “s=%q(#{s})”,s.map{|i|i}[1]

Thanks Daniel, that is perfect – I did not know you could index an NA
with an Array that way – its perfect for my needs (plus it keeps the
type of the Array).

pth