**Good Afternoon / Evening AFL Experts**,

Inspired by this Tradestation function (source openly available as .ELD )

```
{Gaussian Filter}
Inputs: Price(NumericSeries), iptPeriod(NumericSimple), iptPoles(NumericSimple);
variables: aa(0), b(0), w(0), x(0), y(0), y1(0), y2(0), y3(0), y4(0),
a_1(0), a_12(0), a_13(0), a_14(0), a2(0), a3(0), a4(0), Pi(3.141592654),
sqrtOf2(1.414213562), Period(2), poles(0);
if (iptPeriod < 2) then
Period = 2
else
Period = iptPeriod;
// Number of filter poles must be between 1 and 4, inclusive
if iptPoles < 1 then
poles = 1
else if iptPoles > 4 then
poles = 4
else
poles = iptPoles;
// initialization - performed only for first bar
if CurrentBar = 1 then
begin
w = 2 * Pi / Period; // omega
w = 180 * w / Pi; // in degrees
b = (1 - cosine(w)) / (power(sqrtOf2, 2.0/poles) - 1.0);
aa = -b + squareroot(b*b + 2*b);
a_1 = 1.0 - aa;
a_12 = a_1 * a_1;
a_13 = a_1 * a_1 * a_1;
a_14 = a_12 * a_12;
a2 = aa * aa;
a3 = aa * aa * aa;
a4 = a2 * a2;
y1 = Price;
y2 = y1;
y3 = y2;
y4 = y3;
end;
{ Calculate your indicator value here }
x = Price;
if (poles = 1) then
y = aa * x + a_1 * y1
else if (poles = 2) then
y = a2 * x + 2 * a_1 * y1 - a_12 * y2
else if (poles = 3) then
y = a3 * x + 3 * a_1 * y1 - 3 * a_12 * y2 + a_13 * y3
else if (poles = 4) then
y = a4 * x + 4 * a_1 * y1 - 6 * a_12 * y2 + 4 * a_13 * y3 - a_14 * y4;
y4 = y3; // delayed by four bars
y3 = y2; // delayed by three bars
y2 = y1; // delayed by two bars
y1 = y; // delayed by one bar
Gauss = y;
```

Without access to KB or other function narratives amidst the server issue, this is my hit-and-trial in AFL:

```
n = BarCount;
function fact( num )
{
a = 1;
nn = IIf( num <= 1, 1, num );
for( i = 1; i <= nn; i++ )
{
a = a * i;
}
return a;
}
function getPoles( f, Poles, alpha )
{
filt = f;
_sign = 1;
results = 0 + n;
for( r = 1; r <= Max( Min( Poles, n ), 1 ); r++ )
{
mult = fact( Poles ) / ( fact( Poles - r ) * fact( r ) );
matPo = ( 1 - alpha ) ^ r;
prev = Nz( filt[ r - 1 ], 0 );
_Sum = _sign * mult * matPo * prev;
results = results + _Sum;
_sign = _sign * -1;
}
return results - n;
}
function Gauss( Price, Lag, PoleNum )
{
Pi = 3.141592653589793238462643;
beta = ( 1 - cos( 2 * Pi / Lag ) ) / ( ( sqrt( 2 ) ^ ( 2 / PoleNum ) ) - 1 );
alfa = -beta + sqrt( beta * beta + 2 * beta );
pre = Nz( Price, 0 ) * ( alfa ^ PoleNum );
_Filter = pre;
result = IIf( n > 0, getPoles( Ref( _Filter, -1 ), PoleNum, alfa ), 0 );
_Filter = pre + result;
return _Filter;
}
_SECTION_BEGIN( "Gauss Filter" );
Plot( Gauss( ( H + L ) / 2, 13, 8 ), "Gauss", colorWhite, styleLine );
_SECTION_END();
```

Please help to share an efficient and correct way to calculate the Gauss filter using AFL.

Thank you