fonction ecarttype en php

[mat]

Je l'ai cherché partout, je ne l'ai pas trouvé, alors je l'ai
écrite.

Si ça peut servir à d'autres ...

echo "Calcul d'un ecart type";
echo "<br>";

$datas = array("11","22" ,"45","67","21" ,"3","20");

$ecart = ecarttype($data s);

if ($ecart)
{
echo $ecart;
}
else
{
echo "Jeu de valeurs incohérent !";
}

function ecarttype($arra y, $nbdecimals=2) {

if (is_array($arra y))
{
//moyenne des valeurs
reset($array);
$somme=0;
$nbelement=coun t($array);
foreach ($array as $value) {
$somme += floatval($value );
}
$moyenne = $somme/$nbelement;
//numerateur
reset($array);
$sigma=0;
foreach ($array as $value) {
$sigma += pow((floatval($ value)-$moyenne),2);
}
//denominateur = $nbelement
$ecarttype = sqrt($sigma/$nbelement);
return number_format($ ecarttype, $nbdecimals);
}
else
{
return false;
}
}

[R. Rajesh Jeba Anbiah]

Caclulation of standard deviation (Was Re: fonction ecarttype en php)

mat wrote:[color=blue]
> Je l'ai cherché partout, je ne l'ai pas trouvé, alors je l'ai
> écrite.
>
> Si ça peut servir à d'autres ...[/color]
<snip>

Thanks. Would be nice, if you could use English in future. Got it
translated with Google:
<Google translation
url="http://translate.googl e.com/translate?u=htt p://groups.google.c om/group/comp.lang.php/msg/b4524aca9cf1ca5 d&langpair=fr%7 Cen&hl=en&ie=UT F8">

I sought it everywhere, I did not find it, then I have it
written.

If that can be used for others...

echo "Calculatio n of a standard deviation";
echo "< Br >";

$$datas = array("11", "22"," 45", "67"," 21 ", "3"," 20");

$$ecart = ecarttype($data s);

yew ($$ecart)
{
echo $$ecart;
}

else
{
echo "incoherent Set of values!";

}

function ecarttype($arra y, $$nbdecimals=2) {

yew (is_array($arra y))
{
// average of the values
reset($array);
$$somme=0;
$$nbelement=cou nt($array);
foreach ($$array have $$value) {
$$somme + = floatval($value );
}
$$moyenne = $$somme/$nbelement;
// numerator
reset($array);
$$sigma=0;
foreach ($$array have $$value) {
$$sigma + = pow((floatval($ value)-$moyenne),2);
}
// denominator = $$nbelement
$$ecarttype = sqrt($sigma/$nbelement);
return number_format($ ecarttype, $$nbdecimals);
}
else
{
return false;
}
}
</Google translation>

--
<?php echo 'Just another PHP saint'; ?>
Email: rrjanbiah-at-Y!com Blog: http://rajeshanbiah.blogspot.com/

[Christopher Pomasl]

Re: Caclulation of standard deviation (Was Re: fonction ecarttype en php)

On Tue, 30 Aug 2005 07:33:03 -0700, R. Rajesh Jeba Anbiah wrote:
[color=blue]
> mat wrote:[color=green]
>> Je l'ai cherché partout, je ne l'ai pas trouvé, alors je l'ai
>> écrite.
>>
>> Si ça peut servir à d'autres ...[/color]
> <snip>
>
> Thanks. Would be nice, if you could use English in future. Got it
> translated with Google:
> <Google translation
> url="http://translate.googl e.com/translate?u=htt p://groups.google.c om/group/comp.lang.php/msg/b4524aca9cf1ca5 d&langpair=fr%7 Cen&hl=en&ie=UT F8">
>
> I sought it everywhere, I did not find it, then I have it
> written.
>
> If that can be used for others...
>
> echo "Calculatio n of a standard deviation";
> echo "< Br >";
>
> $$datas = array("11", "22"," 45", "67"," 21 ", "3"," 20");
>
> $$ecart = ecarttype($data s);
>
> yew ($$ecart)
> {
> echo $$ecart;
> }
>
> else
> {
> echo "incoherent Set of values!";
>
> }
>
> function ecarttype($arra y, $$nbdecimals=2) {
>
> yew (is_array($arra y))
> {
> // average of the values
> reset($array);
> $$somme=0;
> $$nbelement=cou nt($array);
> foreach ($$array have $$value) {
> $$somme + = floatval($value );
> }
> $$moyenne = $$somme/$nbelement;
> // numerator
> reset($array);
> $$sigma=0;
> foreach ($$array have $$value) {
> $$sigma + = pow((floatval($ value)-$moyenne),2);
> }
> // denominator = $$nbelement
> $$ecarttype = sqrt($sigma/$nbelement);
> return number_format($ ecarttype, $$nbdecimals);
> }
> else
> {
> return false;
> }
> }
> </Google translation>[/color]


Also Note there are two calculations for standard deviation.
The first as shown above is called the "population " deviation and implies
that the sample used to calculate the deviation is the entire sample.

This is defined as sqrt( sum ((x - mean(x))**2) / N)

There is a weighted "sample" deviation calculation which implies that the
sample used is just that, a sample and NOT the entire population.

This is defined as sqrt( sum ((x - mean(2))**2) / N - 1)

In this case, the code shown above should subtract 1 from $nbelement
before the sqtr() function near the bottom.

Chris

[Manuel Lemos]

Re: Caclulation of standard deviation (Was Re: fonction ecarttypeen php)

Hello,

on 08/30/2005 11:09 PM Christopher Pomasl said the following:[color=blue]
> Also Note there are two calculations for standard deviation.
> The first as shown above is called the "population " deviation and implies
> that the sample used to calculate the deviation is the entire sample.
>
> This is defined as sqrt( sum ((x - mean(x))**2) / N)
>
> There is a weighted "sample" deviation calculation which implies that the
> sample used is just that, a sample and NOT the entire population.
>
> This is defined as sqrt( sum ((x - mean(2))**2) / N - 1)
>
> In this case, the code shown above should subtract 1 from $nbelement
> before the sqtr() function near the bottom.[/color]

You may also want to take a look at this class that computes standard
deviation:

http://www.phpclasses.org/probabilistic

--

Regards,
Manuel Lemos

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