[General Information]

Function Name=Pow2P2	; name show up in the select function dialog
Brief Description=two-parameter power function
Function Type=Built-in		; source type, built-in, user-defined, external dll
Function Form=Expression	; function form;
Function Source=fgroup.Pow2P2
Number Of Parameters=2
Number Of Independent Variables=1
Number Of Dependent Variables=1


[Fitting Parameters]

Naming Method=user-defined
Names=a,b
Lower bounds=--,--
Upper bounds=--,--
Meanings=coefficient,power


[Independent Variables]

x = 


[Dependent Variables]

y = default


[Constants]


[Formula]

y = a*(1 + x)^b

[Constraints]

[Parameters Initialization]
sort(x_y_curve);
//smooth(x_y_curve, 2);
a=yatxmin(x_y_curve);
double flag=min(y_data);
if (flag>0) x_y_curve = ln(x_y_curve);
else x_y_curve=ln(-x_y_curve);
Dataset dx;
x_y_curve.AttachX(dx);
dx=ln(1+dx);
double coeff[2];
fitpoly(x_y_curve,1,coeff);
if(flag>0) 
  a=exp(coeff[0]);
else
  a=-exp( coeff[0] );
b=coeff[1];

[Initializations]


[After fitting]


[Controls]
General Linear Constraints=Off
Initialization scripts=Off
Scripts After fitting=Off
