Hello, everyone.
Would be grateful if someone can tell, how can I do shortly (mb with one
method) from such example array
[“a”, “b”, “a”, “c”, “c”, “b”, “b”]
The result
a => 2
b => 3
c => 2
So, to count number of occurances
Hello,
So, to count number of occurences
arr = [“a”, “b”, “a”, “c”, “c”, “b”, “b”]
=> [“a”, “b”, “a”, “c”, “c”, “b”, “b”]h = Hash.new(0) ; arr.each {|e| h[e] += 1}; p h
{“a”=>2, “b”=>3, “c”=>2}
=> nil
Cheers,
Jean-Julien F., thanks.
Maybe have an idea of a one-line version? 
Jean-Julien F. wrote:
2010/7/20 Vitaliy Y. [email protected]:
Jean-Julien F., thanks.
Maybe have an idea of a one-line version?Well: quite the same using inject:
arr.inject(Hash.new(0)) {|h,e| h[e]+= 1; h}
It all depends on what you call ‘one-line’ :o)
Cheers,
Wow, Inject is cool method, thanks !
In my mind one-line is that dows not have semi-coloms or new lines of
course
On Jul 20, 2010, at 10:58 AM, Vitaliy Y. wrote:
Cheers,
Wow, Inject is cool method, thanks !
In my mind one-line is that dows not have semi-coloms or new lines of
course
Soo… that has a semi-colon and isn’t then a one-liner?? 
-Rob
Rob B.
[email protected] http://AgileConsultingLLC.com/
[email protected] http://GaslightSoftware.com/
Rob B. wrote:
Soo… that has a semi-colon and isn’t then a one-liner??
Yeah, not perfectly one-liner. But it is without dot-chain breaking, not
bad too
h = Hash.new(0)
[“a”, “b”, “a”, “c”, “c”, “b”, “b”].each {|s| h[s] += 1};
Nice!
arr.inject(Hash.new(0)) {|h,e| h[e]+= 1; h}
2010/7/20 Vitaliy Y. [email protected]:
Jean-Julien F., thanks.
Maybe have an idea of a one-line version?
Well: quite the same using inject:
arr.inject(Hash.new(0)) {|h,e| h[e]+= 1; h}
It all depends on what you call ‘one-line’ :o)
Cheers,
2010/7/20 Vitaliy Y. [email protected]:
Rob B. wrote:
Soo… that has a semi-colon and isn’t then a one-liner??
Yeah, not perfectly one-liner. But it is without dot-chain breaking, not
bad too
That would be a real one-liner if I could recall how to convert
elegantly an array of size2 arrays into an hash:
arr.group_by {|o| o}.collect{|k,v| [k,v.size]}
Cheers,
On Tue, Jul 20, 2010 at 11:25 PM, Vitaliy Y. [email protected]
wrote:
Jean-Julien F., thanks.
Maybe have an idea of a one-line version?
Try this or something like this.
I’m very sleepy ZZZZZZZZZZZ
arr = [“a”, “b”, “a”, “c”, “c”, “b”, “b”]
p Hash[*(arr.uniq.map{|x| [x,arr.select{|y| y == x}.length]}).flatten]
#> {“a”=>2, “b”=>3, “c”=>2}
Harry
On Tue, Jul 20, 2010 at 2:47 PM, Vitaliy Y. [email protected]
wrote:
… Would be grateful if someone can tell, how can I do shortly (mb with
one
method) from such example array
[“a”, “b”, “a”, “c”, “c”, “b”, “b”]
The result: a => 2, b => 3, c => 2. So, to count number of occurances.
def owtdi( ary ); h = Hash.new(0); ary.each {|e| h[e] += 1}; h; end
def owtdi2( ary ); ary.inject(Hash.new(0)) {|h,e| h[e]+= 1; h}; end
def tmtowtdi( ary )
ary = ary.sort; test_v = ! ary[0]; cary = []; kt = nil
ary.each do |vv|
if vv != test_v then
cary << [test_v, kt] if kt
test_v = vv; kt = 0
end
kt += 1
end
cary << [test_v, kt] if kt
cary
end
rr = [“a”, “b”, “a”, “c”, “c”, “b”, “b”]
p owtdi( rr ), owtdi2( rr ), tmtowtdi( rr )
kt = 100_000
require “benchmark”
ow = ow2 = tmtow = nil
Benchmark.bmbm do|b|
b.report(“owtdi”) { kt.times { ow = owtdi( rr ) } }
b.report(“tmtowtdi”) { kt.times { tmtow = tmtowtdi( rr ) } }
end
puts; p ow, tmtow
END
{“a”=>2, “b”=>3, “c”=>2}
[[“a”, 2], [“b”, 3], [“c”, 2]]
user system total real
ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
owtdi 3.572000 0.016000 3.588000 ( 4.422000)
tmtowtdi 4.883000 0.031000 4.914000 ( 5.819000)
ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32]
owtdi 2.558000 0.047000 2.605000 ( 3.243000)
tmtowtdi 1.545000 0.015000 1.560000 ( 1.943000)
another 1.9.1 run: owtdi user = 2.293 and tmtowtdi user = 1.810;
jruby 1.5.0.RC1 (ruby 1.8.7 patchlevel 249) (2010-04-14 0b08bc7)
(Java HotSpot™ Client VM 1.6.0_14) [x86-java]
owtdi 1.980000 0.000000 1.980000 ( 1.979000)
tmtowtdi 1.523000 0.000000 1.523000 ( 1.522000)
I ought to point out that in a subsequent JRuby run
owtdi user = 1.625 and tmtowtdi user = 1.809,
and in another run owtdi user = 2.118 and tmtowtdi user = 1.987,
so quite variable! But there was quite a lot of apparently random and
purposeless disk i/o going on while the benchmarks were running. (Thank
you,
Windows Vista!) So I would place even less reliance than usual on these
benchmarks. But using inject does seem significantly slower, especially
so
using 1.8.6.
2010/7/20 Harry K. [email protected]:
p Hash[*(arr.uniq.map{|x| [x,arr.select{|y| y == x}.length]}).flatten]
Harry showed the way:
Hash[arr.group_by {|o| o}.collect{|k,v| [k,v.size]}]
=> {“a”=>2, “b”=>3, “c”=>2}
Cheers,
Check this out
[‘a’, ‘b’, ‘a’, ‘b’, ‘c’, ‘c’,
‘c’].group_by{|o|o}.collect{|k,v|{k,v.size}}.to_yaml"
Result:
- a: 2
- b: 2
- c: 3
Hi –
On Wed, 21 Jul 2010, Vitaliy Y. wrote:
Rob B. wrote:
Soo… that has a semi-colon and isn’t then a one-liner??
Yeah, not perfectly one-liner. But it is without dot-chain breaking, not
bad too
In Ruby 1.9 there’s Enumerator#with_object, which is a nice way to avoid
that “; h” thing that you have to do in #inject to make it return the
accumulator:
count_hash = a.each.with_object(Hash.new(0)) {|e, hash| hash[e] += 1
}
David
–
David A. Black, Senior Developer, Cyrus Innovation Inc.
The Ruby training with Black/Brown/McAnally
Compleat Philadelphia, PA, October 1-2, 2010
Rubyist http://www.compleatrubyist.com
On Tue, Jul 20, 2010 at 8:32 AM, Colin B.
[email protected] wrote:
benchmarks. But using inject does seem significantly slower, especially so
using 1.8.6.
I know this isn’t what the original post was about…but…
The variability is probably due partially to the jitting behavior of
the JVM; it’s hard to know when the JVM will hit its stable state.
FWIW, a longer run will get even faster, and passing --server to JRuby
boosts it too:
jruby Java 6 server, fifth iteration:
user system total real
owtdi 0.223000 0.000000 0.223000 ( 0.223000)
tmtowtdi 0.223000 0.000000 0.223000 ( 0.223000)
ruby 1.9.2 trunkish:
user system total real
owtdi 0.470000 0.010000 0.480000 ( 0.481433)
tmtowtdi 0.350000 0.000000 0.350000 ( 0.350423)
I don’t have an explanation for the performance difference; the logic
involved should be pretty native-lib heavy.
- Charlie
David M. wrote:
Hash.new(0).tap{|h| arr.each{|e| h[e] += 1} }
Yes ! I always use this construct. Instead of
obj = Klass.new
do something to obj
obj
I use
Klass.new do |obj|
do something to obj
end
which, at least to me, has a better look.
_md
On Tuesday, July 20, 2010 10:05:27 am Rob B. wrote:
It all depends on what you call ‘one-line’ :o)
Cheers,
Wow, Inject is cool method, thanks !
In my mind one-line is that dows not have semi-coloms or new lines of
courseSoo… that has a semi-colon and isn’t then a one-liner??
If that really bothers anyone…
Hash.new(0).tap{|h| arr.each{|e| h[e] += 1} }