Re: [Flashcoders] Producing a random list with no repeats
Here's a very clean, fast and simple way to randomize an array.
array.sort(randomizeFunction);
function randomize(a:int, b:int):int
{
return int(Math.random() * 2) - 1;
}
If you're not happy with Math.random()'s randomness, there are plenty of other
random number generators out there, such as:
http://lab.polygonal.de/2007/04/21/a-good-pseudo-random-number-generator-prng/
And Grant Skinner's Rndm:
http://www.gskinner.com/blog/archives/2008/01/source_code_see.html
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Re: [Flashcoders] Producing a random list with no repeats
Steven, sorry to contradict you, but although your code is simple and sort
of works, there a couple of problems with it.
First, the sorting function is wrong. A sorting function is supposed to
return -1,0 or 1. But it only returns -1 or 0.
The problem is you are coercing the result to int. You should use Math.round
instead.
int(Math.random() * 2) will return 1 or 0, never 2, because the biggest
value Math.random will return will be close to 1, but never will be 1. So,
if Math.random returns say, 0.9, after you multiply you get 1.8; since
you're using int(), decimals will just be discarded (instead of rounded) and
the result will be 1. There's no way you'll get 2, only 1 or 0. Then you
substract 1, so your sorting function will return either -1 or 0.
Second, you don't need to sort the whole list. It's much more work than it's
needed to shuffle the array. While the Fisher-Yates algorithm is linear, the
sort is not. That is, if you have 40 items, you know the Fisher-Yates will
visit each list slot only once. That's not the case with the sort method.
It grows exponentially. Well, maybe not exactly exponential, I'm not
possitive, but it's not linear anyway, as this code shows:
var list:Array = [];
var numItems:int = 40;
for(var i:int = 0; i numItems; i++) {
list[i] = i;
}
var calls:int = 0;
function randomize(a:int, b:int):int
{
calls++;
return int(Math.random() * 2) - 1;
}
list.sort(randomize);
trace(calls: + calls);
Change numItems and you'll see what I mean. Bottom line, you're doing more
work than you need: you're calling a function instead of doing your
comparison inline and you are calling Math.random more than it's actually
needed to sort the list.
Third, the sorting algorithm works under the assumption that given two
objects they allways sort the same: either the first one is less than, equal
or greater than the second. That doesn't hold true if your sorting function
returns a random result. And I think maybe that's why the number of calls
that the above code prints vary even when you have the same number of items.
Cheers
Juan Pablo Califano
PS. I also used the method you describe (for years) until I read about its
problems, so I thought maybe this is a good opportunity to pass this info
on. To be honest, though, I don't think it will be a problem
preformance-wise unless you have a rather big array.
2010/5/9 Steven Sacks flash...@stevensacks.net
Here's a very clean, fast and simple way to randomize an array.
array.sort(randomizeFunction);
function randomize(a:int, b:int):int
{
return int(Math.random() * 2) - 1;
}
If you're not happy with Math.random()'s randomness, there are plenty of
other random number generators out there, such as:
http://lab.polygonal.de/2007/04/21/a-good-pseudo-random-number-generator-prng/
And Grant Skinner's Rndm:
http://www.gskinner.com/blog/archives/2008/01/source_code_see.html
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Re: [Flashcoders] Producing a random list with no repeats
You're right. I was careless on two counts.
Fisher-Yates it is.
On 5/9/2010 4:36 PM, Juan Pablo Califano wrote:
Steven, sorry to contradict you, but although your code is simple and sort
of works, there a couple of problems with it.
First, the sorting function is wrong. A sorting function is supposed to
return -1,0 or 1. But it only returns -1 or 0.
The problem is you are coercing the result to int. You should use Math.round
instead.
int(Math.random() * 2) will return 1 or 0, never 2, because the biggest
value Math.random will return will be close to 1, but never will be 1. So,
if Math.random returns say, 0.9, after you multiply you get 1.8; since
you're using int(), decimals will just be discarded (instead of rounded) and
the result will be 1. There's no way you'll get 2, only 1 or 0. Then you
substract 1, so your sorting function will return either -1 or 0.
Second, you don't need to sort the whole list. It's much more work than it's
needed to shuffle the array. While the Fisher-Yates algorithm is linear, the
sort is not. That is, if you have 40 items, you know the Fisher-Yates will
visit each list slot only once. That's not the case with the sort method.
It grows exponentially. Well, maybe not exactly exponential, I'm not
possitive, but it's not linear anyway, as this code shows:
var list:Array = [];
var numItems:int = 40;
for(var i:int = 0; i numItems; i++) {
list[i] = i;
}
var calls:int = 0;
function randomize(a:int, b:int):int
{
calls++;
return int(Math.random() * 2) - 1;
}
list.sort(randomize);
trace(calls: + calls);
Change numItems and you'll see what I mean. Bottom line, you're doing more
work than you need: you're calling a function instead of doing your
comparison inline and you are calling Math.random more than it's actually
needed to sort the list.
Third, the sorting algorithm works under the assumption that given two
objects they allways sort the same: either the first one is less than, equal
or greater than the second. That doesn't hold true if your sorting function
returns a random result. And I think maybe that's why the number of calls
that the above code prints vary even when you have the same number of items.
Cheers
Juan Pablo Califano
PS. I also used the method you describe (for years) until I read about its
problems, so I thought maybe this is a good opportunity to pass this info
on. To be honest, though, I don't think it will be a problem
preformance-wise unless you have a rather big array.
2010/5/9 Steven Sacksflash...@stevensacks.net
Here's a very clean, fast and simple way to randomize an array.
array.sort(randomizeFunction);
function randomize(a:int, b:int):int
{
return int(Math.random() * 2) - 1;
}
If you're not happy with Math.random()'s randomness, there are plenty of
other random number generators out there, such as:
http://lab.polygonal.de/2007/04/21/a-good-pseudo-random-number-generator-prng/
And Grant Skinner's Rndm:
http://www.gskinner.com/blog/archives/2008/01/source_code_see.html
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Re: [Flashcoders] Producing a random list with no repeats
PS 2: I think the correct way to write the function that returns a number in
the range -1 / 1 is:
Math.floor(Math.random * 3) - 1
In this case, you could indeed use int() instead of a static Math method, so
I guess I was wrong about your function needing a Math.round call.
2010/5/9 Juan Pablo Califano califa010.flashcod...@gmail.com
Steven, sorry to contradict you, but although your code is simple and sort
of works, there a couple of problems with it.
First, the sorting function is wrong. A sorting function is supposed to
return -1,0 or 1. But it only returns -1 or 0.
The problem is you are coercing the result to int. You should use
Math.round instead.
int(Math.random() * 2) will return 1 or 0, never 2, because the biggest
value Math.random will return will be close to 1, but never will be 1. So,
if Math.random returns say, 0.9, after you multiply you get 1.8; since
you're using int(), decimals will just be discarded (instead of rounded) and
the result will be 1. There's no way you'll get 2, only 1 or 0. Then you
substract 1, so your sorting function will return either -1 or 0.
Second, you don't need to sort the whole list. It's much more work than
it's needed to shuffle the array. While the Fisher-Yates algorithm is
linear, the sort is not. That is, if you have 40 items, you know the
Fisher-Yates will visit each list slot only once. That's not the case with
the sort method. It grows exponentially. Well, maybe not exactly
exponential, I'm not possitive, but it's not linear anyway, as this code
shows:
var list:Array = [];
var numItems:int = 40;
for(var i:int = 0; i numItems; i++) {
list[i] = i;
}
var calls:int = 0;
function randomize(a:int, b:int):int
{
calls++;
return int(Math.random() * 2) - 1;
}
list.sort(randomize);
trace(calls: + calls);
Change numItems and you'll see what I mean. Bottom line, you're doing more
work than you need: you're calling a function instead of doing your
comparison inline and you are calling Math.random more than it's actually
needed to sort the list.
Third, the sorting algorithm works under the assumption that given two
objects they allways sort the same: either the first one is less than, equal
or greater than the second. That doesn't hold true if your sorting function
returns a random result. And I think maybe that's why the number of calls
that the above code prints vary even when you have the same number of items.
Cheers
Juan Pablo Califano
PS. I also used the method you describe (for years) until I read about its
problems, so I thought maybe this is a good opportunity to pass this info
on. To be honest, though, I don't think it will be a problem
preformance-wise unless you have a rather big array.
2010/5/9 Steven Sacks flash...@stevensacks.net
Here's a very clean, fast and simple way to randomize an array.
array.sort(randomizeFunction);
function randomize(a:int, b:int):int
{
return int(Math.random() * 2) - 1;
}
If you're not happy with Math.random()'s randomness, there are plenty of
other random number generators out there, such as:
http://lab.polygonal.de/2007/04/21/a-good-pseudo-random-number-generator-prng/
And Grant Skinner's Rndm:
http://www.gskinner.com/blog/archives/2008/01/source_code_see.html
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Re: [Flashcoders] Producing a random list with no repeats
In the exception that Math.random() returns 1, in which case you would get 2. I don't use Math.random(), though, I use the Parker-Miller PRNG. On 5/9/2010 5:01 PM, Juan Pablo Califano wrote: PS 2: I think the correct way to write the function that returns a number in the range -1 / 1 is: Math.floor(Math.random * 3) - 1 In this case, you could indeed use int() instead of a static Math method, so I guess I was wrong about your function needing a Math.round call. ___ Flashcoders mailing list Flashcoders@chattyfig.figleaf.com http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
Re: [Flashcoders] Producing a random list with no repeats
If that happens, it's a bug in the player. From the docs: Returns a pseudo-random number n, where 0 = n 1. So, the biggest number random returns can approximate 1, but should never be 1. What I got wrong in my original answer was that multiplying by 2 and then rounding introduces a bias towards 1 (and then if you substract 1, the bias is towards 0). Think about it this way: You've got a number between 0 and 1.9 when you do Math.random * 2. That is, a number that can get very close to 2, but never be actually 2. If you round it you'll get: 0 for 0...0.49 1 for 0.5...1.49 2 for 1.5...19 The actual numbers might not be exact as I'm not sure what's the boundary for rounding up or down; I'm also considering only two decimals for simplicity. But anyway, the distribution is obviously not even. There's about a 0.25 chance of getting 0, the same chance of getting 2, but the double, 0.5, of getting 1. However, if you multiply by 3 and floor the result (or coerce it to int for that matter), you get rid of the bias: Math.random * 3 will give a number in the range 0...2.99 So, if you get rid of the decimal part, you have: 0 for 0...0.99 1 for 1...1.99 2 for 2...2.99 Which gives a result that's clearly more evenly distributed than the first approach. 2010/5/9 Steven Sacks flash...@stevensacks.net In the exception that Math.random() returns 1, in which case you would get 2. I don't use Math.random(), though, I use the Parker-Miller PRNG. On 5/9/2010 5:01 PM, Juan Pablo Califano wrote: PS 2: I think the correct way to write the function that returns a number in the range -1 / 1 is: Math.floor(Math.random * 3) - 1 In this case, you could indeed use int() instead of a static Math method, so I guess I was wrong about your function needing a Math.round call. ___ Flashcoders mailing list Flashcoders@chattyfig.figleaf.com http://chattyfig.figleaf.com/mailman/listinfo/flashcoders ___ Flashcoders mailing list Flashcoders@chattyfig.figleaf.com http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
Re: [Flashcoders] Producing a random list with no repeats
Hi,
here an alternative way of producing a random array:
/**
* Randomizes a copy of this array.
*/
public function randomize (pArray:Array):Array {
var newArray:Array = pArray.slice();
var i:Number = newArray.length;
while (i) {
var p:Number = random(i);
var t:Object = newArray[--i];
newArray[i] = newArray[p];
newArray[p] = t;
}
return newArray;
}
regards
JC
On Thu, May 6, 2010 at 3:27 AM, Juan Pablo Califano
califa010.flashcod...@gmail.com wrote:
A simple way:
Put all the candidate numbers in a list (in this case, 1 to 40). Then pick
randomly from that array, one at the time, and make sure you remove that
number from the candidates list, so you can't have duplicates.
In code (untested):
function getRandomList():Array {
var min:Number = 1;
var max:Number = 40;
var numItems:Number = 10;
var candidates:Array = [];
// fill up the candidates list with the eligible numbers
for(var i:Number = min; i = max; i++) {
candidates.push(i);
}
var list:Array = [];
var idx:Number = 0;
var selectedNumber:Number = 0;
for(i = 0; i numItems; i++) {
// get a number from the candidates list, randomly. Add it to the
result and remove it from the candidates list (using splice)
idx = Math.floor(Math.random() * candidates.length);
selectedNumber = candidates.splice(idx,1)[0];
list.push(selectedNumber);
}
return list;
}
Cheers
Juan Pablo Califano
2010/5/5 Alan Neilsen aneil...@gotafe.vic.edu.au
I am working in ActionScript 2. I want to create a quiz in which 10
questions are randomly selected from a block of 40 questions. I found the
following code, but I can't work out how to stop it doubling up the
questions.
function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random() * (max - min + 1)) +
min;
return randomNum;
}
for (var i = 0; i 10; i++) {
var n:Number = randRange(1, 40)
trace(n);
}
When I run this it outputs a list of numbers like 40 13 17 12 27 12
3
17 9 15 which means some questions (in this case 17 and 12) will
appear
twice in my quiz.
Bearing in mind that I am a bit of an ActionScript dummy, can anybody
suggest a way to modify the above script to prevent the same number being
generated more than once.
This message is for the named person’s use only. It may contain
confidential, proprietary or legally privileged information. No
confidentiality or privilege is waived or; lost by any mistransmission.
If
you receive this message in error, please immediately delete it and all
copies of it from your system, destroy any hard copies of it and notify
the sender. You must not directly or indirectly, use, disclose,
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Re: [Flashcoders] Producing a random list with no repeats
ah my bad , i think this is probably the same as fisher yates;)
On Fri, May 7, 2010 at 12:20 PM, Hans Wichman
j.c.wich...@objectpainters.com wrote:
Hi,
here an alternative way of producing a random array:
/**
* Randomizes a copy of this array.
*/
public function randomize (pArray:Array):Array {
var newArray:Array = pArray.slice();
var i:Number = newArray.length;
while (i) {
var p:Number = random(i);
var t:Object = newArray[--i];
newArray[i] = newArray[p];
newArray[p] = t;
}
return newArray;
}
regards
JC
On Thu, May 6, 2010 at 3:27 AM, Juan Pablo Califano
califa010.flashcod...@gmail.com wrote:
A simple way:
Put all the candidate numbers in a list (in this case, 1 to 40). Then pick
randomly from that array, one at the time, and make sure you remove that
number from the candidates list, so you can't have duplicates.
In code (untested):
function getRandomList():Array {
var min:Number = 1;
var max:Number = 40;
var numItems:Number = 10;
var candidates:Array = [];
// fill up the candidates list with the eligible numbers
for(var i:Number = min; i = max; i++) {
candidates.push(i);
}
var list:Array = [];
var idx:Number = 0;
var selectedNumber:Number = 0;
for(i = 0; i numItems; i++) {
// get a number from the candidates list, randomly. Add it to the
result and remove it from the candidates list (using splice)
idx = Math.floor(Math.random() * candidates.length);
selectedNumber = candidates.splice(idx,1)[0];
list.push(selectedNumber);
}
return list;
}
Cheers
Juan Pablo Califano
2010/5/5 Alan Neilsen aneil...@gotafe.vic.edu.au
I am working in ActionScript 2. I want to create a quiz in which 10
questions are randomly selected from a block of 40 questions. I found
the
following code, but I can't work out how to stop it doubling up the
questions.
function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random() * (max - min + 1)) +
min;
return randomNum;
}
for (var i = 0; i 10; i++) {
var n:Number = randRange(1, 40)
trace(n);
}
When I run this it outputs a list of numbers like 40 13 17 12 27 12
3
17 9 15 which means some questions (in this case 17 and 12) will
appear
twice in my quiz.
Bearing in mind that I am a bit of an ActionScript dummy, can anybody
suggest a way to modify the above script to prevent the same number
being
generated more than once.
This message is for the named person’s use only. It may contain
confidential, proprietary or legally privileged information. No
confidentiality or privilege is waived or; lost by any mistransmission.
If
you receive this message in error, please immediately delete it and all
copies of it from your system, destroy any hard copies of it and notify
the sender. You must not directly or indirectly, use, disclose,
distribute, print or copy any part of this message if you are not the
intended recipient. GOULBURN OVENS INSTITUTE OF TAFE and
any of its subsidiaries each reserve the right to monitor all e-mail
communications through its networks. Any views expressed in this
message are those of the individual sender, except where the
message states otherwise and the sender is authorised to state them
to be the views of any such entity.
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Re: [Flashcoders] Producing a random list with no repeats
I always use Fisher-Yates shuffle method to randomise an Array, which
yields more unbiased result.
http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
My AS3 interpretation of Fisher-Yates is as follows; I can just call
this from anywhere in my scripts ;)
package utils {
public function fisherYates(arr:Array):void {
var i:uint = arr.length;
while(--i){
var j:uint = Math.floor(Math.random()*(i + 1));
var tmpI:Object = arr[i];
var tmpJ:Object = arr[j];
arr[i] = tmpJ;
arr[j] = tmpI;
}
}
}
--
Kenneth Kawamoto
http://www.materiaprima.co.uk/
On 6 May 2010 02:27, Juan Pablo Califano
califa010.flashcod...@gmail.com wrote:
A simple way:
Put all the candidate numbers in a list (in this case, 1 to 40). Then pick
randomly from that array, one at the time, and make sure you remove that
number from the candidates list, so you can't have duplicates.
In code (untested):
function getRandomList():Array {
var min:Number = 1;
var max:Number = 40;
var numItems:Number = 10;
var candidates:Array = [];
// fill up the candidates list with the eligible numbers
for(var i:Number = min; i = max; i++) {
candidates.push(i);
}
var list:Array = [];
var idx:Number = 0;
var selectedNumber:Number = 0;
for(i = 0; i numItems; i++) {
// get a number from the candidates list, randomly. Add it to the
result and remove it from the candidates list (using splice)
idx = Math.floor(Math.random() * candidates.length);
selectedNumber = candidates.splice(idx,1)[0];
list.push(selectedNumber);
}
return list;
}
Cheers
Juan Pablo Califano
2010/5/5 Alan Neilsen aneil...@gotafe.vic.edu.au
I am working in ActionScript 2. I want to create a quiz in which 10
questions are randomly selected from a block of 40 questions. I found the
following code, but I can't work out how to stop it doubling up the
questions.
function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random() * (max - min + 1)) +
min;
return randomNum;
}
for (var i = 0; i 10; i++) {
var n:Number = randRange(1, 40)
trace(n);
}
When I run this it outputs a list of numbers like 40 13 17 12 27 12 3
17 9 15 which means some questions (in this case 17 and 12) will appear
twice in my quiz.
Bearing in mind that I am a bit of an ActionScript dummy, can anybody
suggest a way to modify the above script to prevent the same number being
generated more than once.
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RE: [Flashcoders] Producing a random list with no repeats
/**
* Generates an array of random numbers from 1 or 0 to max
where all numbers through max are used, and no number is zero (if specified).
* Specify true if no zeros are to be included, specify false
if zeros are to be included in the resulting array.
* @param max the maximum range for the numbers.
* @param useZero Specify true if no zeros are to be
included, specify false if zeros are to be included in the resulting array.
* @return an array of random numbers where no number is the
same.
* */
public static function rndNumArray(max:int,
useZero:Boolean=false):Array
{
var array:Array = [];
for (var i1:int = 0; i1 max; i1++)
{
array.push();
}
var i2:int = 0;
while (i2 array.length)
{
var rndNum:Number = rndNum(0, max);
if (!containedInArray(rndNum, array) )
{
//if (useZero) rndNum = rndNum-1;
array[i2] = rndNum;
i2++;
}
}
if (useZero)
{
var arrLen:int = array.length;
for (var i3:int = 0; i3 arrLen; i3++)
{
array[i3] = array[i3]-1;
}
}
return array;
}
/**
* Generates a random number within the given range.
*
* @example listing version=3.0
* var myRandomNumber:Number = rndNum(2, 13);br/
* trace(myRandomNumber); //returns 7 (a random between 2 and
13)
* /listing
* @param minVal the minimum number for the range.
* @param maxVal the maxiumum number for the range.
* @return returns the random number generated.
*
* */
public static function rndNum(minVal:Number,
maxVal:Number):Number
{
return minVal +
Math.floor(Math.random()*(maxVal+1-minVal));
}
Jason Merrill
Bank of America Global Learning
Learning Performance Solutions
Join the Bank of America Flash Platform Community and visit our Instructional
Technology Design Blog
(note: these are for Bank of America employees only)
-Original Message-
From: flashcoders-boun...@chattyfig.figleaf.com
[mailto:flashcoders-boun...@chattyfig.figleaf.com] On Behalf Of
kennethkawam...@gmail.com
Sent: Thursday, May 06, 2010 5:03 AM
To: Flash Coders List
Subject: Re: [Flashcoders] Producing a random list with no repeats
I always use Fisher-Yates shuffle method to randomise an Array, which yields
more unbiased result.
http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
My AS3 interpretation of Fisher-Yates is as follows; I can just call this from
anywhere in my scripts ;)
package utils {
public function fisherYates(arr:Array):void {
var i:uint = arr.length;
while(--i){
var j:uint = Math.floor(Math.random()*(i + 1));
var tmpI:Object = arr[i];
var tmpJ:Object = arr[j];
arr[i] = tmpJ;
arr[j] = tmpI;
}
}
}
--
Kenneth Kawamoto
http://www.materiaprima.co.uk/
On 6 May 2010 02:27, Juan Pablo Califano califa010.flashcod...@gmail.com
wrote:
A simple way:
Put all the candidate numbers in a list (in this case, 1 to 40). Then
pick randomly from that array, one at the time, and make sure you
remove that number from the candidates list, so you can't have duplicates.
In code (untested):
function getRandomList():Array {
var min:Number = 1;
var max:Number = 40;
var numItems:Number = 10;
var candidates:Array = [];
// fill up the candidates list with the eligible numbers
for(var i:Number = min; i = max; i++) {
candidates.push(i);
}
var list:Array = [];
var idx:Number = 0;
var selectedNumber:Number = 0;
for(i = 0; i numItems; i++) {
// get a number from the candidates list, randomly. Add it to
the result and remove it from the candidates list (using splice)
idx = Math.floor(Math.random() * candidates.length);
selectedNumber = candidates.splice(idx,1)[0];
list.push(selectedNumber
Re: [Flashcoders] Producing a random list with no repeats
It's probably best just to create an Array or Vector containing numbers 1 to 40. (Vectors are only available in AS3, not sure about Array). Shuffle the array, then choose the first 10 elements. A reasonably effective way to shuffle an array is to step through the array, and for each element swap it with some other randomly selected element. Another approach is to start with an array whose elements contain numbers 1 through 40. Randomly select one of the 40 elements, record its value, and remove it from the array. Now you have 39 elements. Randomly select one of the 39 elements, record its value, and remove it from the array. Continue in this fashion until you've selected 10 elements. The worst approach is to repeatedly generate random numbers in the range 1 through 40, and add the number your list of questions only if it's not already on the list. The reason this approach is bad is that the execution time is unpredictable - you could be 'rolling the dice' hundreds of times and always getting numbers that are already on your list. On 2010-05-06 , at 08:45 , Alan Neilsen wrote: I am working in ActionScript 2. I want to create a quiz in which 10 questions are randomly selected from a block of 40 questions. I found the following code, but I can't work out how to stop it doubling up the questions. ___ Flashcoders mailing list Flashcoders@chattyfig.figleaf.com http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
Re: [Flashcoders] Producing a random list with no repeats
Hi Allen,
Just a thought, but maybe have the quiz numbers set in an array that
the var n:Number is retrieved and have the min and max that the
random code calls match the amount of items in the array.
After selecting a question, remove it from the array, thus the array
length (max) reduces and the random code still works, but the
previous questions are no longer in the array to choose from.
var numArray:Array = new Array();
numArray = [40, 20, 35, 4, 5, 9];
var currentNum:Number = null;
function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random(max, min));
return randomNum;
}
for (var i = 0; i numArray.length; i++) {
var n:Number = randRange(0, numArray.length);
currentNum = numArray[n];
numArray = numArray.splice(n);
trace(incrament number: +i);
trace(currentNum: +currentNum);
trace(numArray: +numArray);
}
This was off the top of the head, so you will need to test it.
HTH,
Karl
On May 5, 2010, at 7:45 PM, Alan Neilsen wrote:
I am working in ActionScript 2. I want to create a quiz in which 10
questions are randomly selected from a block of 40 questions. I
found the following code, but I can't work out how to stop it
doubling up the questions.
function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random() * (max - min +
1)) + min;
return randomNum;
}
for (var i = 0; i 10; i++) {
var n:Number = randRange(1, 40)
trace(n);
}
When I run this it outputs a list of numbers like 40 13 17 12
27 12 3 17 9 15 which means some questions (in this case 17
and 12) will appear twice in my quiz.
Bearing in mind that I am a bit of an ActionScript dummy, can
anybody suggest a way to modify the above script to prevent the
same number being generated more than once.
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Re: [Flashcoders] Producing a random list with no repeats
A simple way:
Put all the candidate numbers in a list (in this case, 1 to 40). Then pick
randomly from that array, one at the time, and make sure you remove that
number from the candidates list, so you can't have duplicates.
In code (untested):
function getRandomList():Array {
var min:Number = 1;
var max:Number = 40;
var numItems:Number = 10;
var candidates:Array = [];
// fill up the candidates list with the eligible numbers
for(var i:Number = min; i = max; i++) {
candidates.push(i);
}
var list:Array = [];
var idx:Number = 0;
var selectedNumber:Number = 0;
for(i = 0; i numItems; i++) {
// get a number from the candidates list, randomly. Add it to the
result and remove it from the candidates list (using splice)
idx = Math.floor(Math.random() * candidates.length);
selectedNumber = candidates.splice(idx,1)[0];
list.push(selectedNumber);
}
return list;
}
Cheers
Juan Pablo Califano
2010/5/5 Alan Neilsen aneil...@gotafe.vic.edu.au
I am working in ActionScript 2. I want to create a quiz in which 10
questions are randomly selected from a block of 40 questions. I found the
following code, but I can't work out how to stop it doubling up the
questions.
function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random() * (max - min + 1)) +
min;
return randomNum;
}
for (var i = 0; i 10; i++) {
var n:Number = randRange(1, 40)
trace(n);
}
When I run this it outputs a list of numbers like 40 13 17 12 27 12 3
17 9 15 which means some questions (in this case 17 and 12) will appear
twice in my quiz.
Bearing in mind that I am a bit of an ActionScript dummy, can anybody
suggest a way to modify the above script to prevent the same number being
generated more than once.
This message is for the named person’s use only. It may contain
confidential, proprietary or legally privileged information. No
confidentiality or privilege is waived or; lost by any mistransmission. If
you receive this message in error, please immediately delete it and all
copies of it from your system, destroy any hard copies of it and notify
the sender. You must not directly or indirectly, use, disclose,
distribute, print or copy any part of this message if you are not the
intended recipient. GOULBURN OVENS INSTITUTE OF TAFE and
any of its subsidiaries each reserve the right to monitor all e-mail
communications through its networks. Any views expressed in this
message are those of the individual sender, except where the
message states otherwise and the sender is authorised to state them
to be the views of any such entity.
#
This e-mail message has been scanned for Viruses and Content and cleared
by MailMarshal
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