It is a complex function, functions are quoted frequently, you may read from bottom up The independent variable for final fit is q
%%Rg0 is a function of L and b Rg0sq<-function(L,b)L*b/6*(1-3/2*b/L+3/2*(b/L)^2-3/4*(b/L)^3*(1-exp(-2*L/b))) %%alpha is a defined function alpha<-function(x)(1+(x/3.12)^2+(x/8.67)^3)^(0.176/3) %%w is a defined function w<-function(x)(1+tanh(x-1.523)/0.1477)/2 %%It is Rg^2 Rgsq<-function(L,b)(alpha(L/b)*Rg0sq(L,b)) %%This is Rg Rg<-function(L,b)(Rg0sq(L,b))^0.5 %%A debye function of q, the parameters are L and b PDebye<-function(L,b)2*(exp(-q^2*Rg0sq(L,b))+q^2*Rg0sq(L,b)-1)/q^4/(Rg0sq(L,b))^2 %%Another function of q that quote w, PDebye, Rg, parameters are v, L and b Pexv<-function(v,L,b)w(q*Rg(L,b))*PDebye(L,b)+(1-w(q*Rg(L,b)))(1.22*(q*Rg(L,b))^(-1/v)+0.4288*(q*Rg(L,b))^(-2/v)-1.651*(q*Rg(L,b))^(-1/v)) %%Another defined function cf<-function(L,b,pa,pb)pa/(L/b)^pb %%A function of q, quote Pexv, Rgsq, cf Psfcex<-function(v,L,b,pa,pb)Pexv(v,L,b)+cf(L,b,pa,pb)*b/L/15*(4+7/q^2/Rgsq(L,b)-(11+7/q^2/Rgsq(L,b))*exp(-q^2*Rgsq(L,b))) %%non-linear fit Pfit<-function(p)sum((I-Psfcex(p[1],p[2],p[3],p[4],p[5]))^2) wavefit<-nlm(Pfit,c(1.5,500,5,1,0.1),hessian=TRUE) error code: Error in c(1.5, 500, 5, 1, 0.1) : unused argument(s) (0.1) the fifth parameter is pb, which goes from Psfcex to alpha, actually L,b and pa in alpha are used, why not pb? -- View this message in context: http://r.789695.n4.nabble.com/unsued-argument-tp4640034.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.