Need help to custom the rand function ,

Hi guys,

I was wondering how could i get a random number exemple between 1 and
100 but with n% of getting some value over a number x.

Thanks a lot in advance.

Fred

Re: Need help to custom the rand function ,

Fred wrote:
> Hi guys,
>
> I was wondering how could i get a random number exemple between 1 and
> 100 but with n% of getting some value over a number x.
>
> Thanks a lot in advance.
>
> Fred
>

If you want n% chance of getting a value over x, then it isn't a random
number.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

Re: Need help to custom the rand function ,

On 31 jan, 14:05, Jerry Stuckle wrote:
> Fred wrote:
> > Hi guys,
>
> > I was wondering how could i get a random number exemple between 1 and
> > 100 but with n% of getting some value over a number x.
>
> > Thanks a lot in advance.
>
> > Fred
>
> If you want n% chance of getting a value over x, then it isn't a random
> number.
>
> --
> ==================
> Remove the "x" from my email address
> Jerry Stuckle
> JDS Computer Training Corp.
> jstuck...@attglobal.net
> ==================

Wow man that help me a lot =)

Seriously can you point me somewhere that could help ?

Thanks

Re: Need help to custom the rand function ,

Fred wrote:
> Hi guys,
>
> I was wondering how could i get a random number exemple between 1 and
> 100 but with n% of getting some value over a number x.
>
> Thanks a lot in advance.
>
> Fred

Never mind Jerry, No one else does.


So you want a random number from a weighted distribution?


Your spec doesn't contain quite enough data to formulate the formula,
since there are an infinite number of distributions that have N% over
value X..

One example, is that you first of all get a random number between 0 and
100: If this is greater than N, then select a random number greater than
X, else select one less than X.

So in pseudo code where RAND(X) returns a number between 0 and X-1...


if ((RAND(100))

Re: Need help to custom the rand function ,

On 31 jan, 14:29, The Natural Philosopher wrote:
> Fred wrote:
> > Hi guys,
>
> > I was wondering how could i get a random number exemple between 1 and
> > 100 but with n% of getting some value over a number x.
>
> > Thanks a lot in advance.
>
> > Fred
>
> Never mind Jerry, No one else does.
>
> So you want a random number from a weighted distribution?
>
> Your spec doesn't contain quite enough data to formulate the formula,
> since there are an infinite number of distributions that have N% over
> value X..
>
> One example, is that you first of all get a random number between 0 and
> 100: If this is greater than N, then select a random number greater than
> X, else select one less than X.
>
> So in pseudo code where RAND(X) returns a number between 0 and X-1...
>
> if ((RAND(100))
Thanks for the info, i wont mind on him then =)

Almost there with the code,

Let me add some real number in the exemple :

i know before the random what number i must have over let take 50 for
the exemple,
i also need the random to still pick between 0 and 100, but with a
chance of 60% (exemple) to draw something over 50 .

Thanks

Re: Need help to custom the rand function ,

Fred wrote:
> On 31 jan, 14:29, The Natural Philosopher wrote:
>> Fred wrote:
>>> Hi guys,
>>> I was wondering how could i get a random number exemple between 1 and
>>> 100 but with n% of getting some value over a number x.
>>> Thanks a lot in advance.
>>> Fred
>> Never mind Jerry, No one else does.
>>
>> So you want a random number from a weighted distribution?
>>
>> Your spec doesn't contain quite enough data to formulate the formula,
>> since there are an infinite number of distributions that have N% over
>> value X..
>>
>> One example, is that you first of all get a random number between 0 and
>> 100: If this is greater than N, then select a random number greater than
>> X, else select one less than X.
>>
>> So in pseudo code where RAND(X) returns a number between 0 and X-1...
>>
>> if ((RAND(100)) >
> Thanks for the info, i wont mind on him then =)
>
> Almost there with the code,
>
> Let me add some real number in the exemple :
>
> i know before the random what number i must have over let take 50 for
> the exemple,
> i also need the random to still pick between 0 and 100, but with a
> chance of 60% (exemple) to draw something over 50 .
>
> Thanks
>

Actually, the troll "Natural Philosopher" is one one who should be
ignored. He seldom has anything to say that is correct. I was just
pointing out you really aren't looking for a random number, from your
description. Maybe a minor point to you, but very important when
creating an algorithm.

The real question here is, what kind of distribution do you want? For
example, do you want a linear distribution, an exponential or
logarithmic distribution, or like you said here, a 60% chance of being
over 50?

In the case you cited, you want 1-50 to occur 40% of the time, and
51-100 to occur 60% of the time (approximately). Something like this
might work (not tested but the algorithm should work):

function notReallyRand() (
$temp = mt_rand(0,999);
if ($temp < 400)
return intval($temp/8);
else
return intval((($temp-400) / 12) + 50);
}

It gets a random number between 0 and 999. If the random number is
between 0 and 399 (inclusive), it returns value / 8 as an int (0-49).

If the value is >= 400, it subtracts 400 from the value (0-599) and
divides by 12 (0-49.xx). It add 50 to this and returns the int value
(50-99).

You can adjust values as necessary.




--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

Re: Need help to custom the rand function ,

On Jan 31, 8:56 pm, Fred wrote:
> Hi guys,
>
> I was wondering how could i get a random number exemple between 1 and
> 100 but with n% of getting some value over a number x.
>
> Thanks a lot in advance.
>
> Fred

Here is the code ;)

for($i=1;$i<=100;$i++){
$rnum=rand(1,100);
if($rnum>x)
$bigx++;
else $smallx++;
$count++;
}
$ratio=$bigx/$count;
echo "Ratio of the created random numbers bigger than x is :" .
$ratio;

Re: Need help to custom the rand function ,

On 31 Jan, 19:29, The Natural Philosopher wrote:
> Fred wrote:
> > Hi guys,
>
> > I was wondering how could i get a random number exemple between 1 and
> > 100 but with n% of getting some value over a number x.
>
> > Thanks a lot in advance.
>
> > Fred
>
> Never mind Jerry, No one else does.
>
> So you want a random number from a weighted distribution?
>
> Your spec doesn't contain quite enough data to formulate the formula,
> since there are an infinite number of distributions that have N% over
> value X..
>
> One example, is that you first of all get a random number between 0 and
> 100: If this is greater than N, then select a random number greater than
> X, else select one less than X.
>
> So in pseudo code where RAND(X) returns a number between 0 and X-1...
>
> if ((RAND(100))
This is not a god way to get a weighted distribution (and the OP is
NOT asking for a weighted distribution) - you should just generate one
floating point number and apply a transformation function to it.
Continuous transformations are quite difficult but since for a
possible range of 100 integer values a discontinuous transformation
would be adequate - something like:

function transform($in)
{
if (($in<0) || ($in>100)) trigger_error('out of range');
$mul=array(
1=>10, 5=>9, 10=>7, 15=>6....40=>1, 50=>0.9, 55=>0.8...
);
return($in * $mul[5*(integer)($in/20)]);
}

Note the values above will emphasize the mean rather than what the OP
was asking for, but could be adapted for purpose by tweaking the $mul
values.

C.

Re: Need help to custom the rand function ,

C. (http://symcbean.blogspot.com/) wrote:
> On 31 Jan, 19:29, The Natural Philosopher wrote:
>> Fred wrote:
>>> Hi guys,
>>> I was wondering how could i get a random number exemple between 1 and
>>> 100 but with n% of getting some value over a number x.
>>> Thanks a lot in advance.
>>> Fred
>> Never mind Jerry, No one else does.
>>
>> So you want a random number from a weighted distribution?
>>
>> Your spec doesn't contain quite enough data to formulate the formula,
>> since there are an infinite number of distributions that have N% over
>> value X..
>>
>> One example, is that you first of all get a random number between 0 and
>> 100: If this is greater than N, then select a random number greater than
>> X, else select one less than X.
>>
>> So in pseudo code where RAND(X) returns a number between 0 and X-1...
>>
>> if ((RAND(100)) >
> This is not a god way to get a weighted distribution (and the OP is
> NOT asking for a weighted distribution)

(a) I never said it was.
(b) Agreed. But some weighting is inherent in what he said he wanted.
(c) it is one way to get what he said he wanted though.

The problam is he wnats SOME form of weighted distribution, ..as evinced
by the actual spec. But there isn't enough to say WHAT weighting he wants.

- you should just generate one
> floating point number and apply a transformation function to it.
> Continuous transformations are quite difficult but since for a
> possible range of 100 integer values a discontinuous transformation
> would be adequate - something like:
>
> function transform($in)
> {
> if (($in<0) || ($in>100)) trigger_error('out of range');
> $mul=array(
> 1=>10, 5=>9, 10=>7, 15=>6....40=>1, 50=>0.9, 55=>0.8...
> );
> return($in * $mul[5*(integer)($in/20)]);
> }
>
> Note the values above will emphasize the mean rather than what the OP
> was asking for, but could be adapted for purpose by tweaking the $mul
> values.
>

Indeed.

> C.

Re: Need help to custom the rand function ,

On 31 jan, 21:39, Jerry Stuckle wrote:
> Fred wrote:
> > On 31 jan, 14:29, The Natural Philosopher wrote:
> >> Fred wrote:
> >>> Hi guys,
> >>> I was wondering how could i get a random number exemple between 1 and
> >>> 100 but with n% of getting some value over a number x.
> >>> Thanks a lot in advance.
> >>> Fred
> >> Never mind Jerry, No one else does.
>
> >> So you want a random number from a weighted distribution?
>
> >> Your spec doesn't contain quite enough data to formulate the formula,
> >> since there are an infinite number of distributions that have N% over
> >> value X..
>
> >> One example, is that you first of all get a random number between 0 and
> >> 100: If this is greater than N, then select a random number greater than
> >> X, else select one less than X.
>
> >> So in pseudo code where RAND(X) returns a number between 0 and X-1...
>
> >> if ((RAND(100)) >
> > Thanks for the info, i wont mind on him then =)
>
> > Almost there with the code,
>
> > Let me add some real number in the exemple :
>
> > i know before the random what number i must have over let take 50 for
> > the exemple,
> > i also need the random to still pick between 0 and 100, but with a
> > chance of 60% (exemple) to draw something over 50 .
>
> > Thanks
>
> Actually, the troll "Natural Philosopher" is one one who should be
> ignored. He seldom has anything to say that is correct. I was just
> pointing out you really aren't looking for a random number, from your
> description. Maybe a minor point to you, but very important when
> creating an algorithm.
>
> The real question here is, what kind of distribution do you want? For
> example, do you want a linear distribution, an exponential or
> logarithmic distribution, or like you said here, a 60% chance of being
> over 50?
>
> In the case you cited, you want 1-50 to occur 40% of the time, and
> 51-100 to occur 60% of the time (approximately). Something like this
> might work (not tested but the algorithm should work):
>
> function notReallyRand() (
> $temp = mt_rand(0,999);
> if ($temp < 400)
> return intval($temp/8);
> else
> return intval((($temp-400) / 12) + 50);
>
> }
>
> It gets a random number between 0 and 999. If the random number is
> between 0 and 399 (inclusive), it returns value / 8 as an int (0-49).
>
> If the value is >= 400, it subtracts 400 from the value (0-599) and
> divides by 12 (0-49.xx). It add 50 to this and returns the int value
> (50-99).
>
> You can adjust values as necessary.
>
> --
> ==================
> Remove the "x" from my email address
> Jerry Stuckle
> JDS Computer Training Corp.
> jstuck...@attglobal.net
> ==================

Thats exaclty the kind of algorythm i needed thanks a lot man , you
should have said that first =)
Ive tweak it a bit and its doiing a great job !

Thanks again !

Fred

Re: Need help to custom the rand function ,

Fred wrote:
> On 31 jan, 21:39, Jerry Stuckle wrote:
>> Fred wrote:
>>> On 31 jan, 14:29, The Natural Philosopher wrote:
>>>> Fred wrote:
>>>>> Hi guys,
>>>>> I was wondering how could i get a random number exemple between 1 and
>>>>> 100 but with n% of getting some value over a number x.
>>>>> Thanks a lot in advance.
>>>>> Fred
>>>> Never mind Jerry, No one else does.
>>>> So you want a random number from a weighted distribution?
>>>> Your spec doesn't contain quite enough data to formulate the formula,
>>>> since there are an infinite number of distributions that have N% over
>>>> value X..
>>>> One example, is that you first of all get a random number between 0 and
>>>> 100: If this is greater than N, then select a random number greater than
>>>> X, else select one less than X.
>>>> So in pseudo code where RAND(X) returns a number between 0 and X-1...
>>>> if ((RAND(100)) >>> Thanks for the info, i wont mind on him then =)
>>> Almost there with the code,
>>> Let me add some real number in the exemple :
>>> i know before the random what number i must have over let take 50 for
>>> the exemple,
>>> i also need the random to still pick between 0 and 100, but with a
>>> chance of 60% (exemple) to draw something over 50 .
>>> Thanks
>> Actually, the troll "Natural Philosopher" is one one who should be
>> ignored. He seldom has anything to say that is correct. I was just
>> pointing out you really aren't looking for a random number, from your
>> description. Maybe a minor point to you, but very important when
>> creating an algorithm.
>>
>> The real question here is, what kind of distribution do you want? For
>> example, do you want a linear distribution, an exponential or
>> logarithmic distribution, or like you said here, a 60% chance of being
>> over 50?
>>
>> In the case you cited, you want 1-50 to occur 40% of the time, and
>> 51-100 to occur 60% of the time (approximately). Something like this
>> might work (not tested but the algorithm should work):
>>
>> function notReallyRand() (
>> $temp = mt_rand(0,999);
>> if ($temp < 400)
>> return intval($temp/8);
>> else
>> return intval((($temp-400) / 12) + 50);
>>
>> }
>>
>> It gets a random number between 0 and 999. If the random number is
>> between 0 and 399 (inclusive), it returns value / 8 as an int (0-49).
>>
>> If the value is >= 400, it subtracts 400 from the value (0-599) and
>> divides by 12 (0-49.xx). It add 50 to this and returns the int value
>> (50-99).
>>
>> You can adjust values as necessary.
>>
>> --
>> ==================
>> Remove the "x" from my email address
>> Jerry Stuckle
>> JDS Computer Training Corp.
>> jstuck...@attglobal.net
>> ==================
>
> Thats exaclty the kind of algorythm i needed thanks a lot man , you
> should have said that first =)
> Ive tweak it a bit and its doiing a great job !
>
> Thanks again !
>
> Fred
>

I would have - had you been clear about what you wanted!

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================