weighted random a la SC "[1,2,4].wchoose([0.5,0.3,0.1]);" in Max

good example of where syntax shines and patching gets ugly.
(although you're wrong about the auto normalisation - that'd be
[1,2,4].wchoose([0.5,0.3,0.1].normalizeSum); to be really picky)
simplest i don't know, but one way to do it would be with chained
[split] or [if] statements. of course this would mean to hardcode
the number of elements in the lists. arbitrary length is a bit more
complicated. perhaps there's already a Lobject for it - or you could
code something fairly easily in javascript/java.

_f

Am 16.02.2008 um 23:02 schrieb Klaas-Jan Govaart:

>
> Hello,
>
> What would be the simplest way to implement a weighted random in
> Max, comparable to the following line of SuperCollider code?
>
> [1,2,4].wchoose([0.5,0.3,0.1]);
>
> The line results in a value of 1, 2 or 3, where the weighting is:
> 1 five times more often than 4, and 2 three times more often than 4.
>
> In SC the values for the weighting don't have to add up to one,
> they are automatically normalized. They just have to be smaller
> than 1.
>
> I am aware of the possibilities of the [table] object, but am
> looking for something a bit cleaner, that can use floats et cetera.
> Ideally an object that would take two lists (values/weightings) and
> output a value when banged.
>
> Any thoughts would be appreciated.
>
> Regards,
> Klaas-Jan

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Quote: f wrote on Sun, 17 February 2008 00:18
----------------------------------------------------
> good example of where syntax shines and patching gets ugly.

yes, isn't it. Wouldn't it be great to have an object like expr in which you could dump a line of SC code in cases like this?

SCexpr is on my wishlist for Max 5.1 ;)

> (although you're wrong about the auto normalisation - that'd be
> [1,2,4].wchoose([0.5,0.3,0.1].normalizeSum); to be really picky)

Oops! Of course, you are right. I just remembered it was very easy, but of course not "autocomplete_my_thought mode = 1" easy.

> simplest i don't know, but one way to do it would be with chained
> [split] or [if] statements. of course this would mean to hardcode
> the number of elements in the lists. arbitrary length is a bit more
> complicated. perhaps there's already a Lobject for it - or you could
> code something fairly easily in javascript/java.

Thanks for the example, but this is already getting "uglier" than I was hoping for.
Especially the hardcoded length of the list I don't like. Could be scripted I guess, but it would be hardly elegant.

Thanks again!
Klaas-Jan

Use quantile function with table object

On 2/16/08 5:02 PM, "Klaas-Jan Govaart" wrote:

>
> Hello,
>
> What would be the simplest way to implement a weighted random in Max,
> comparable to the following line of SuperCollider code?
>
> [1,2,4].wchoose([0.5,0.3,0.1]);
>
> The line results in a value of 1, 2 or 3, where the weighting is:
> 1 five times more often than 4, and 2 three times more often than 4.
>
> In SC the values for the weighting don't have to add up to one, they are
> automatically normalized. They just have to be smaller than 1.
>
> I am aware of the possibilities of the [table] object, but am looking for
> something a bit cleaner, that can use floats et cetera. Ideally an object that
> would take two lists (values/weightings) and output a value when banged.
>
> Any thoughts would be appreciated.
>
> Regards,
> Klaas-Jan
>
>
>
>

Cheers
Gary Lee Nelson
Oberlin College
www.timara.oberlin.edu/GaryLeeNelson

Weights smaller than 1. & two lists

On 2/16/08 5:02 PM, "Klaas-Jan Govaart" wrote:

>
> Hello,
>
> What would be the simplest way to implement a weighted random in Max,
> comparable to the following line of SuperCollider code?
>
> [1,2,4].wchoose([0.5,0.3,0.1]);
>
> The line results in a value of 1, 2 or 3, where the weighting is:
> 1 five times more often than 4, and 2 three times more often than 4.
>
> In SC the values for the weighting don't have to add up to one, they are
> automatically normalized. They just have to be smaller than 1.
>
> I am aware of the possibilities of the [table] object, but am looking for
> something a bit cleaner, that can use floats et cetera. Ideally an object that
> would take two lists (values/weightings) and output a value when banged.
>
> Any thoughts would be appreciated.
>
> Regards,
> Klaas-Jan
>
>
>
>

Cheers
Gary Lee Nelson
Oberlin College
www.timara.oberlin.edu/GaryLeeNelson

Thank you for your input Gary, but I'm still looking for something other than table though. It just can't be use with floats, really.
In this patch I tried inputting some floats, trying to get them back out with only two decimal points of resolution. Quickly hitting the table limit of 16383 though, of course..

Any thoughts on what I could use besides table?

here is one where you can change the weights automatically

save this one as flux in patches

flux help window:

Sorry for the misunderstanding. Your original message seemed to indicate
that you were selecting only from ints.

Try this urn-like algorithm.

Build a list that has n copies of each value where n represents the weight.
1 5 2 3 4 1 would become 1 1 1 1 1 2 2 2 4
Scramble that list to something like 1 2 1 2 2 1 1 4
Cycle through the scrambled list taking and removing each item in turn.
When the list is empty, refill it and scramble again.

On 2/17/08 12:12 AM, "Klaas-Jan Govaart" wrote:

>
> Thank you for your input Gary, but I'm still looking for something other than
> table though. It just can't be use with floats, really.
> In this patch I tried inputting some floats, trying to get them back out with
> only two decimal points of resolution. Quickly hitting the table limit of
> 16383 though, of course..
>
> Any thoughts on what I could use besides table?
>
>

Cheers
Gary Lee Nelson
Oberlin College
www.timara.oberlin.edu/GaryLeeNelson

basic javascript solution...

///////save as wchoose.js

// /f0 080217

//weights should add up to one for it to function properly
//both lists (weights and values) should be equal in length

inlets= 2;
setinletassist(0, "bang, list");
setinletassist(1, "weights");
setoutletassist(0, "the chosen one");
var wlist= new Array();    //weights
var vlist= new Array();    //values

function list() {
    if(inlet==0) {
        vlist= arguments;
    } else {
        wlist= arguments;
    }
}
function bang() {
    var i, sum= 0;
    var r= Math.random();
    for(i= 0; i
        sum= sum+wlist[i];
        if(r
            outlet(0, vlist[i]);
            i= vlist.length;
        }
    }
}

///////test patch

Am 17.02.2008 um 16:13 schrieb Gary Lee Nelson:

> Sorry for the misunderstanding. Your original message seemed to
> indicate
> that you were selecting only from ints.
>
> Try this urn-like algorithm.
>
> Build a list that has n copies of each value where n represents the
> weight.
> 1 5 2 3 4 1 would become 1 1 1 1 1 2 2 2 4
> Scramble that list to something like 1 2 1 2 2 1 1 4
> Cycle through the scrambled list taking and removing each item in
> turn.
> When the list is empty, refill it and scramble again.
>
>
> On 2/17/08 12:12 AM, "Klaas-Jan Govaart" wrote:
>
>>
>> Thank you for your input Gary, but I'm still looking for something
>> other than
>> table though. It just can't be use with floats, really.
>> In this patch I tried inputting some floats, trying to get them
>> back out with
>> only two decimal points of resolution. Quickly hitting the table
>> limit of
>> 16383 though, of course..
>>
>> Any thoughts on what I could use besides table?
>>
>> #P window setfont "Sans Serif" 9.;
>> #P window linecount 1;
>> #P newex 143 426 32 196617 print;
>> #P newex 143 403 41 196617 * 0.01;
>> #P button 143 52 15 0;
>> #P newex 143 137 101 196617 vexpr int($f1*100);
>> #P message 222 157 67 196617 0.5 0.3 0.1;
>> #P message 143 119 151 196617 21.234501 432.345612 7654.566895;
>> #P newex 143 180 89 196617 mxj list.Multiplex;
>> #P newex 203 337 117 196617 expr .5+$f1*1000000.;
>> #P newex 143 294 70 196617 unpack 0 0.;
>> #P button 45 119 15 0;
>> #P newex 45 234 44 196617 uzi 100;
>> #P newex 143 235 55 196617 zl group 2;
>> #P newex 143 207 99 196617 t l clear;
>> #P button 101 234 15 0;
>> #N vtable 16383 20 74 230 241 1 100000 weights;
>> #P newobj 143 363 70 196617 table weights;
>> #P window linecount 2;
>> #P comment 17 363 121 196617 weights store at location
>> corresponding to value;
>> #P window linecount 3;
>> #P comment 57 176 82 196617 100 bangs for table quantil function;
>> #P connect 7 0 6 0;
>> #P connect 14 0 11 0;
>> #P connect 11 0 13 0;
>> #P fasten 13 0 10 0 148 156;
>> #P connect 10 0 4 0;
>> #P connect 4 0 5 0;
>> #P connect 5 0 8 0;
>> #P fasten 6 0 2 0 50 354 148 354;
>> #P fasten 3 0 2 0 106 348 148 348;
>> #P fasten 4 1 2 0 237 321 148 321;
>> #P connect 8 0 2 0;
>> #P connect 2 0 15 0;
>> #P connect 15 0 16 0;
>> #P connect 8 1 9 0;
>> #P connect 9 0 2 1;
>> #P connect 14 0 12 0;
>> #P connect 12 0 10 1;
>
>
> Cheers
> Gary Lee Nelson
> Oberlin College
> www.timara.oberlin.edu/GaryLeeNelson
>
>
>

#|
fredrikolofsson.com klippav.org musicalfieldsforever.com
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