An elegant way to mix arrays arrays…

@Grand_MamamouchMar 06.2005

Hi !

I am looking for an elegant way to mix arrays arrays. Could you give me one, please ?

Thanx for your help !

to post a comment

18 Comments(s) _↴

@Willy_DuittMar 06.2005 — #Like this??

<i>
 </i>array=[ 
 ['Bernard','Bernard'], 
 ['Jean','Jean'], 
 ['Jocelyne','Jocelyne'], 
 ['Maud','Maud'], 
 ['Rudolf','Rudolf'] 
 ] 
 
 function aleate() 
 { 
 return Math.pow(-1, Math.round(2*Math.random())) 
 } 
 
 alert(array.sort(aleate))

.....Willy

@UltimaterMar 06.2005 — #Hi all,

Hi Willy Duitt!

[img]http://boards1.wizards.com/images/smilies/dropjaw.gif[/img]

(This is a simily for some reason my IMG Code is off)

I cannot believe you randomized all the elements of that array

with so few line!

I made a function who's sole-purpose is to do what your function did

in 5 lines!

[code=php]
 Array.prototype.rand=addRandFunction 
 function addRandFunction(){ 
 var DaArray1=this 
 var DaArray2=new Array(DaArray1.length);for(var i=0;i<DaArray1.length;i++){DaArray2[i]=i} 
 var DaArray3=new Array(DaArray1.length); 
 
 for(i=0;i<DaArray1.length;i++){ 
 var picked=Math.floor(Math.random()*DaArray2.length) 
 DaArray3[i]=DaArray1[DaArray2[picked]] 
 delete DaArray2[picked]; 
 
 var New_Array=new Array() 
 var j=0; 
 for(var ii=0;ii<DaArray2.length;ii++){ 
 if(typeof DaArray2[ii]!="undefined"){ 
 New_Array[j]=DaArray2[ii];j++ 
 } 
 } 
 DaArray2=New_Array 
 
 } 
 
 return DaArray3 
 }
 alert([1,2,3].rand())
 [/code]

I even made a whole thread about it [url=http://www.webdeveloper.com/forum/showthread.php?s=&threadid=57731]someArray.rand()[/url]

Nextly I cannot believe you used Math.round and Math.random

together successfully without tilting-the-scale.

I think you got lucky because your statement with Math.pow is flexable,

you could have just as easily have used:

Math.pow(-1, Math.round([color=red]1[/color]*Math.random()))

I'd have used:

Math.pow(-1, Math.floor(Math.random()*2))

But still your chances of producing a [color=blue]-1[/color] or [color=blue]1[/color] didn't change.

Amazing :eek:

Usually Math.round tips-the-scale with Math.random like so:

[color=red][size=+1]alert(Math.round(Math.random()*5))[/size][/color]

Math.round rounds a random number from 0 to 5(excluding 0 and 5).

before round:after round

[color=red]0.0-0.49... :0[/color] (half change)

0.5-1.49... :1

1.5-2.49... :2

2.5-3.49... :3

3.5-4.49... :4

[color=red]4.5-5.00... :5[/color] (half chance)

[color=red][size=+1]alert(Math.floor(Math.random()*6))[/size][/color]

Math.floor [b]always[/b] rounds down and never up un-like Math.round.

Math.floor will floor a random number from 0 to 6(excluding 0 and 6).

before floor:after floor

0.0-0.9... :0

1.0-1.9... :1

2.0-2.9... :2

3.0-3.9... :3

4.0-4.9... :4

5.0-5.9... :5

(6 cannot be pick)

@UltimaterMar 06.2005 — #By the Way,

If you were wondering how I was checking the chances:

[size=-3]

<i>
 </i>&lt;script&gt;
 var pos_ones=0
 var neg_ones=0
 for(i=0;i&lt;10000;i++){
 var rand0=Math.pow(-1, Math.floor(Math.random()*2) ) 
 if(rand0==-1)neg_ones++
 if(rand0==1)pos_ones++
 }
 alert("Math.floorn"+"positive onest"+(pos_ones/100)
 +"%"+"nnegative onest"+(neg_ones/100)+"%")
 
 pos_ones=0
 neg_ones=0
 for(i=0;i&lt;10000;i++){
 var rand1=Math.pow(-1, Math.round(1*Math.random())) 
 if(rand1==-1)neg_ones++
 if(rand1==1)pos_ones++
 }
 alert("Math.roundn"+"positive onest"+(pos_ones/100)
 +"%"+"nnegative onest"+(neg_ones/100)+"%")
 &lt;/script&gt;

[/size]

@Willy_DuittMar 06.2005 — #I didn't write that...

I merely copied it from where the O/P cross-posted the same question on the PHP forum here: ?

http://www.webdeveloper.com/forum/showthread.php?s=&postid=329007#post329007

.....Willy

@UltimaterMar 06.2005 — #Hey Grand Mamamouch,

If randomizing all the element's postions in an array is

[b]not[/b] what you want us to post for you,

please be more specific.

@Willy_DuittMar 06.2005 — #[i]Originally posted by Ultimater [/i]

[B]Hey Grand Mamamouch,

If randomizing all the element's postions in an array is

[b]not[/b] what you want us to post for you,

please be more specific. [/B][/QUOTE]

Seems as if noone actually understands the question...

I wonder if it's homework??

http://www.webxpertz.net/forums/showthread.php?t=32154

http://www.codingforums.com/showthread.php?t=53826

http://www.sitepoint.com/forums/showthread.php?t=240419

.....Willy

@JPnycMar 06.2005 — #I don't think so. He's posted a fair amount here and none of the other questions seemed like homework assignments.

@Grand_MamamouchauthorMar 07.2005 — #Hi all !

and thank you for your contributions !

A clever guy found a better-than-mine aleate fonction :

[code=php]
 array=[
 ['Bernard','Bernard'], 
 ['Jean','Jean'], 
 ['Jocelyne','Jocelyne'],
 ['Maud','Maud'], 
 ['Rudolf','Rudolf']
 ]
 
 function aleate()
 {
 return Math.random()*2 -1 
 }
 
 document.write(array.sort(aleate))
 [/code]

Stays the problem of the inner arrays broken. I want them intact, wich is not the case there. It's not a matter of presentation : i want to use the retrieved array as an array of intact inner arrays.

I would be fullfilled if you find a solution to this problem. It would be a great step for science ;-)

@Grand_MamamouchauthorMar 07.2005 — #My function

[code=php]
 function aleate()
 {
 return 2*Math.random() -1
 }
 [/code]

in the end respects the inner arrays !

Happy day !

@UltimaterMar 07.2005 — #I think Grand Mamamouch wants to randomize the position of all the elements of an array's array(an array inside of an array).

If I understand correctly, he wants to turn:

[['Bernard','Bernard'],

['Jean','Jean'],

['Jocelyne','Jocelyne'],

['Maud','Maud'],

['Rudolf','Rudolf']]

into:

[['Jean','Bernard'],

['Jean','Rudolf'],

['Jocelyne','Maud'],

['Maud','Jocelyne'],

['Rudolf','Bernard']]

@BigMoosieApr 13.2005 — #I'd have used:

Math.pow(-1, Math.floor(Math.random()*2))[/QUOTE]

I'd have used:

2*(Math.round(Math.random())-0.5)

@UltimaterApr 13.2005 — #You really enjoy digging-up the trash, huh? I'm sure that the host's problem has long-long resolved...

Also you can always do this one:

<i>
 </i>Math.round(Math.random())?-1:1

Who cares which method you use to generate a random -1 or 1...

The only valuable difference would be the speed difference, which in that case

would totally defeat the purpose of using the sort

function all-together... For a faster way to randomize all the elements of an array, you'd be able to beat the speed of the sort function by almost 10x with almost any custom-made function...

And I don't feel like finding the link of any such function because the host of this thread has probably long resolved his/her problem.

@7studApr 13.2005 — #Hi all,

But still your chances of producing a [color=blue]-1[/color] or [color=blue]1[/color] didn't change.

Amazing :eek:

Usually Math.round tips-the-scale with Math.random like so:

[color=red][size=+1]alert(Math.round(Math.random()*5))[/size][/color]

Math.round rounds a random number from 0 to 5(excluding 0 and 5).

before round:after round

[color=red]0.0-0.49... :0[/color] (half change)

0.5-1.49... :1

1.5-2.49... :2

2.5-3.49... :3

3.5-4.49... :4

[color=red]4.5-5.00... :5[/color] (half chance)

[color=red][size=+1]alert(Math.floor(Math.random()*6))[/size][/color]

Math.floor [b]always[/b] rounds down and never up un-like Math.round.

Math.floor will floor a random number from 0 to 6(excluding 0 and 6).

before floor:after floor

0.0-0.9... :0

1.0-1.9... :1

2.0-2.9... :2

3.0-3.9... :3

4.0-4.9... :4

5.0-5.9... :5

(6 cannot be pick)[/QUOTE]

By the Way,

If you were wondering how I was checking the chances:[/quote]
If you truly understood what you posted, there would be no need to run a simulation. The probablility distribution is in fact skewed, you just didn't check for all the outcomes, and all the outcomes are used by sort().

@7studApr 13.2005 — #My function

PHP Code:

function aleate()

{

return 2*Math.random() -1

}

in the end respects the inner arrays !
[/quote]
I think Grand Mamamouch wants to randomize the position of all the elements of an array's array(an array inside of an array).

If I understand correctly, he wants to turn:

[['Bernard','Bernard'],

['Jean','Jean'],

['Jocelyne','Jocelyne'],

['Maud','Maud'],

['Rudolf','Rudolf']]

into:

[['Jean','Bernard'],

['Jean','Rudolf'],

['Jocelyne','Maud'],

['Maud','Jocelyne'],

['Rudolf','Bernard']][/quote]
Do you really? To me it's quite obvious that is not what they want. The op said they wanted to respect the inner arrays, and if you take a few secs to run their example, you could see it does just that. Since they said the example does what they want, you are mistaken.

@BigMoosieApr 14.2005 — #You really enjoy digging-up the trash, huh? [/quote]I was searching for a script that does this and when I saw your unusaul approach to gettin +/- 1 I thought I would comment.
Who cares which method you use to generate a random -1 or 1...[/quote]I may be wrong but I think it takes longer to execute Math.pow than to just subtract then multiply.

@UltimaterApr 14.2005 — #If you want the fastest function to do this, I believe it is the following:

[url=http://www.webdeveloper.com/forum/showthread.php?s=&threadid=59096#post331175]http://www.webdeveloper.com/forum/showthread.php?s=&threadid=59096#post331175[/url]

You owe me one for finding that thread... it took 10 full-minutes of my time to find it...

@UltimaterApr 14.2005 — #You might also be interested in this thread: [url=http://www.webdeveloper.com/forum/showthread.php?t=59517]useful tip: sort(function(){})[/url]

@BigMoosieApr 14.2005 — #Thankyou

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