dear list I am student M.S. statistics in department statistics . I am working in the function "nls" in the [R 2.3.1] with 246 data and want to fit the "exp" model to vectors( v and u ) but I have a problem to use it u 5.000000e-13 2.179057e+03 6.537171e+03 1.089529e+04 1.525340e+04 1.961151e+04 2.396963e+04 2.832774e+04 3.268586e+04 3.704397e+04 4.140209e+04 4.576020e+04 5.011831e+04 5.447643e+04 v 8.382562e-01 4.090868e+02 1.311053e+03 2.124143e+03 3.365494e+03 2.138903e+03 7.687774e+03 1.028396e+04 1.004186e+04 2.059798e+04 1.438464e+04 2.861373e+04 2.294919e+04 2.807701e+04 data1<-data.frame(u=u ,v=v) nls(v~c0+(ce*(1-exp((-u)/ae))),data=data1,start=list(c0=0,ce=1000,ae=3000)) Error in nls(v ~ c0 + (ce * (1 - exp((-u)/ae))), data = data1, start = list(c0 = 0, : step factor 0.000488281 reduced below 'minFactor' of 0.000976563 i dont know how to solve it, please help me . best regards Sadeghian --------------------------------- [[alternative HTML version deleted]]