Logistic fit of data set

Function Richards(w,x) : FitFunc
    Wave w
    Variable x
 
    //CurveFitDialog/ These comments were created by the Curve Fitting dialog. Altering them will
    //CurveFitDialog/ make the function less convenient to work with in the Curve Fitting dialog.
    //CurveFitDialog/ Equation:
    //CurveFitDialog/ f(x) = K0+((K1-K0)/(1+K2*exp(-K3*(x-K4)))^(1/K5))
    //CurveFitDialog/ End of Equation
    //CurveFitDialog/ Independent Variables 1
    //CurveFitDialog/ x
    //CurveFitDialog/ Coefficients 6
    //CurveFitDialog/ w[0] = K0
    //CurveFitDialog/ w[1] = K1
    //CurveFitDialog/ w[2] = K2
    //CurveFitDialog/ w[3] = K3
    //CurveFitDialog/ w[4] = K4
    //CurveFitDialog/ w[5] = K5
 
    return w[0]+((w[1]-w[0])/(1+w[2]*exp(-w[3]*(x-w[4])))^(1/w[5]))
End
 
Function Gompertz(w,x) : FitFunc
    Wave w
    Variable x
 
    //CurveFitDialog/ These comments were created by the Curve Fitting dialog. Altering them will
    //CurveFitDialog/ make the function less convenient to work with in the Curve Fitting dialog.
    //CurveFitDialog/ Equation:
    //CurveFitDialog/ f(x) = K0*exp(K1*exp(K2*x))
    //CurveFitDialog/ End of Equation
    //CurveFitDialog/ Independent Variables 1
    //CurveFitDialog/ x
    //CurveFitDialog/ Coefficients 3
    //CurveFitDialog/ w[0] = K0
    //CurveFitDialog/ w[1] = K1
    //CurveFitDialog/ w[2] = K2
 
    return w[0]*exp(w[1]*exp(w[2]*x))
End

Function Logistic_fit(w,x) : FitFunc
    Wave w
    Variable x
 
    //CurveFitDialog/ These comments were created by the Curve Fitting dialog. Altering them will
    //CurveFitDialog/ make the function less convenient to work with in the Curve Fitting dialog.
    //CurveFitDialog/ Equation:
    //CurveFitDialog/ f(x) = 1/(1+exp(-(x-a)/b))
    //CurveFitDialog/ End of Equation
    //CurveFitDialog/ Independent Variables 1
    //CurveFitDialog/ x
    //CurveFitDialog/ Coefficients 2
    //CurveFitDialog/ w[0] = a 
    //CurveFitDialog/ w[1] = b 
  
 
    return statsLogisticCDF(x,w[0],w[1])
End