Greetings R users, maybe there is someone who can help me with this problem: I'm trying to fit this discontinous model : GE<-data.frame( Ci<-c(81,87,91,111,159,173,295,453,629,984), A<-c(-0.9,1.2,3.5,8.3,13.1,14.4,22.9,27.3,29.6,32.6) ) rhs <- function(Ci, Vcmax, J, Rd) { ? ?R <-0.008314472 ? ?Tleaf <-25 ? ?Kc <-exp(38.05-79.43/(R*(Tleaf+273.15))) ? ?Ko <-exp(20.30-36.38/(R*(Tleaf+273.15))) ? ?Gstar <-exp(19.02-38.83/(R*(Tleaf+273.15))) ? ?O <-210 ? ?ge<-min( ?(Vcmax*(Ci-Gstar))/(Ci+(Kc*(1+(O/Ko)))) ,(J*(Ci-Gstar))/((4*Ci)+(8*Gstar)) ?) -Rd ? ?ge ? ?} m<- nls(A ~ rhs(Ci, Vcmax, J, Rd), data=GE, start = list(Vcmax=50, J=150, Rd=4), trace = T) And get the following error: Error in qr(.swts * attr(rhs, "gradient")) : ?dims [product 3] do not match the length of object [10] In addition: Warning messages: 1: In min(x) : no non-missing arguments to min; returning Inf 2: In max(x) : no non-missing arguments to max; returning -Inf 3: In .swts * attr(rhs, "gradient") : ?longer object length is not a multiple of shorter object length Any clues on how can I solve the Inf issue and avoid the error? Thanks, Andre