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Say I've got a string like this:

"{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2, 2.1, 4.2}}"

- imagine it's aspiring to be a list of sublists, with 4 reals in
each list. I want to produce a sorted version:

(1.4 2.2 2.1 4.2)
(2.1 3.14 2.4 2.2)
(3.1 1.3 2.5 2.1)

What would be a good way to do this?

thanks

Pete

On Oct 10, 2005, at 4:46 PM, pete boardman wrote:

> Say I've got a string like this:
>
> "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2, 2.1, 4.2}}"
>
> - imagine it's aspiring to be a list of sublists, with 4 reals in
> each list. I want to produce a sorted version:
>
> (1.4 2.2 2.1 4.2)
> (2.1 3.14 2.4 2.2)
> (3.1 1.3 2.5 2.1)
>
> What would be a good way to do this?

Well, if you can count on the data format, the following is pretty
simple:

irb(main):001:0> arr = eval "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4,
2.2}, {1.4, 2.2, 2.1, 4.2}}".tr("{}", "[]")
=> [[3.1, 1.3, 2.5, 2.1], [2.1, 3.1, 2.4, 2.2], [1.4, 2.2, 2.1, 4.2]]
irb(main):002:0>
irb(main):003:0* arr.sort { |a, b| a.first <=> b.first }
=> [[1.4, 2.2, 2.1, 4.2], [2.1, 3.1, 2.4, 2.2], [3.1, 1.3, 2.5, 2.1]]

Hope that helps.

James Edward Gray II

On Tue, 11 Oct 2005, pete boardman wrote:

> Say I've got a string like this:
>
> "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2, 2.1, 4.2}}"
>
> - imagine it's aspiring to be a list of sublists, with 4 reals in each list.
> I want to produce a sorted version:
>
> (1.4 2.2 2.1 4.2)
> (2.1 3.14 2.4 2.2)
> (3.1 1.3 2.5 2.1)
>
> What would be a good way to do this?

harp:~ > cat a.rb
buf = "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2, 2.1, 4.2}}"
buf.gsub! %r/ { /x, ' [ '
buf.gsub! %r/ } /x, ' ] '

require 'yaml'
list = YAML::load(buf).map{|s| s.sort}.sort

p list

harp:~ > ruby a.rb
[[1.3, 2.1, 2.5, 3.1], [1.4, 2.1, 2.2, 4.2], [2.1, 2.2, 2.4, 3.1]]


-a
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On 10 Oct 2005, at 22:53, James Edward Gray II wrote:

> arr = eval "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2,
> 2.1, 4.2}}".tr("{}", "[]")
> arr.sort { |a, b| a.first <=> b.first }

Thanks, James - simple, elegant, and nearly perfect! Is it easy to
sort the array of arrays by their second, third, and fourth entries
as well:

ie such that

[[2.1, 2.2, 9.5, 2.1], [2.1, 2.2, 2.4, 2.2], [2.1, 2.2, 2.1, 4.2]]

sorts to

[[2.1, 2.2, 2.1, 4.2],[2.1, 2.2, 2.4, 2.2],[2.1, 2.2, 9.5, 2.1]]

rather than

[[2.1, 2.2, 9.5, 2.1], [2.1, 2.2, 2.4, 2.2], [2.1, 2.2, 2.1, 4.2]]

thanks

Pete

pete boardman <> wrote:
> On 10 Oct 2005, at 22:53, James Edward Gray II wrote:
>
> > arr = eval "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2,
> > 2.1, 4.2}}".tr("{}", "[]")
> > arr.sort { |a, b| a.first <=> b.first }
>
> Thanks, James - simple, elegant, and nearly perfect! Is it easy to
> sort the array of arrays by their second, third, and fourth entries
> as well:

That's actually the default behaviour, so you can just say arr.sort

martin

pete boardman wrote:
> Is it easy to
> sort the array of arrays by their second, third, and fourth entries
> as well:
>
> ie such that
>
> [[2.1, 2.2, 9.5, 2.1], [2.1, 2.2, 2.4, 2.2], [2.1, 2.2, 2.1, 4.2]]
>
> sorts to
>
> [[2.1, 2.2, 2.1, 4.2],[2.1, 2.2, 2.4, 2.2],[2.1, 2.2, 9.5, 2.1]]
>
> rather than
>
> [[2.1, 2.2, 9.5, 2.1], [2.1, 2.2, 2.4, 2.2], [2.1, 2.2, 2.1, 4.2]]
>
> thanks
>
> Pete

a = "{{2.1, 2.2, 9.5, 2.1}, {2.1, 2.2, 2.4, 2.2}, {2.1, 2.2, 2.1,
4.2}}"\
[2..-3].split( '}, {' ).map{|x| x.split( /,\s+/ ).map{|s| s.to_f } }
p a.sort

James Edward Gray II wrote:

> irb(main):001:0> arr = eval "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4,
> 2.2}, {1.4, 2.2, 2.1, 4.2}}".tr("{}", "[]")
> => [[3.1, 1.3, 2.5, 2.1], [2.1, 3.1, 2.4, 2.2], [1.4, 2.2, 2.1, 4.2]]
> irb(main):002:0>
> irb(main):003:0* arr.sort { |a, b| a.first <=> b.first }
> => [[1.4, 2.2, 2.1, 4.2], [2.1, 3.1, 2.4, 2.2], [3.1, 1.3, 2.5, 2.1]]

arr.sort_by{|x| x.first }

Thanks for these answers!

Pete

Hi --

On Tue, 11 Oct 2005, William James wrote:

>
> James Edward Gray II wrote:
>
>> irb(main):001:0> arr = eval "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4,
>> 2.2}, {1.4, 2.2, 2.1, 4.2}}".tr("{}", "[]")
>> => [[3.1, 1.3, 2.5, 2.1], [2.1, 3.1, 2.4, 2.2], [1.4, 2.2, 2.1, 4.2]]
>> irb(main):002:0>
>> irb(main):003:0* arr.sort { |a, b| a.first <=> b.first }
>> => [[1.4, 2.2, 2.1, 4.2], [2.1, 3.1, 2.4, 2.2], [3.1, 1.3, 2.5, 2.1]]
>
> arr.sort_by{|x| x.first }

Better yet:

arr.sort

which will handle tie-breaks automatically.


David

--
David A. Black

One more thing - I forgot that I need to get the result back to a
string... So (thanks to your help andn Ruby's 'eval') I can go from
this:

"{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2, 2.1, 4.2}}"

to this:

[[1.4, 2.2, 2.1, 4.2], [2.1, 3.1, 2.4, 2.2], [3.1, 1.3, 2.5, 2.1]]

but I can't persuade the 'p' method to turn this back into a string:

"[[1.4, 2.2, 2.1, 4.2], [2.1, 3.1, 2.4, 2.2], [3.1, 1.3, 2.5, 2.1]]"

(and I should be able to go from here to :

"{{1.4, 2.2, 2.1, 4.2}, {2.1, 3.1, 2.4, 2.2}, {3.1, 1.3, 2.5, 2.1}}"

on my own


Pete