NArray shuffle

[Patrick Hurley]

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

 

[ara.t.howard]

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

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