how to use nlsM minpack R

I have this information:

A   xo   x   y    yo    p_1 p_2 p_3 p_4  s1   s2    s3      s4
1   1.7  1.7 0.45 0.45   1  0   0   0    0.45 #N/A  #N/A    #N/A
1   1.7  2.7 2.49 0.45   1  0   0   0    0.45 #N/A  #N/A    #N/A
2   1.7  1.7 0.48 0.48   0  1   0   0    0.45 0.48  #N/A    #N/A
2   1.7  2.7 3.49 0.48   0  1   0   0    0.45 0.48  #N/A    #N/A 
3   1.7  1.7 0.58 0.58   0  0   1   0    0.45 0.48  0.58    #N/A
3   1.7  2.7 2.19 0.58   0  0   1   0    0.45 0.48  0.58    #N/A

And I wanted to translate the following SAS script to R:

proc model data=five method=MARQUARDT maxiter=1000; 

yo=p1S1+p2S2+...+p&maxi S&maxi;
y=yo*EXP(-(b12)*x**-(b13))/EXP(-(b12)*xo**-(b13))

fit y /converge=0.001 estdata=start outpredict out=resinicial outest=params dw dwprob;
outvars num_parc y yo x xo resid pred actual truque id;

run; %mend fits;

In R I am using the package min.pack doing the following:

library(minpack.lm)
Gfun=function(x,t,G0,t0){ 
  y=yo*exp(-(x[1])*x^-(x[2]))/exp(-(x[1])*xo^-(x[2]))
  return(y)
}

Yresid <- function(parS, yObs, x,yo,xo) { # Resíduos
  YObs-Yfun(parS,x=x,yo=yo,xo=xo)
}

parStart=c(3.405398, 0.40278)


nls.out <- nls.lm(par=parStart, fn = Yresid, YObs = Y, X=X,Yo=Yo,Xo=Xo,
                  control = nls.lm.control(nprint=1,
                                           ftol = .Machine$double.eps,
                                           ptol = .Machine$double.eps,
                                           maxfev=10000, maxiter = 500))

But I get the following error:

  

Error in t ^ - (x [2]): non-numeric argument to binary operator

and I also do not know how to indicate the function of yo=p1S1+p2S2+...+p&maxi S&maxi