Hi, I am a grad student at the university of Louisiana at Lafayette. I have a question. I have an equation with 3 unknowns. f= P/ (r+p) pow(B). I have values of f for different r's. Can i use R to find the P,p,B values which are constants. The equation is Manderbolts equation. Thanks and regards, Sai Charan Komanduru Research Assistant, CACS ULL
>>>>> "KSC" == Komanduru Sai C <Komanduru> writes:KSC> I am a grad student at the university of Louisiana at Lafayette. I have a KSC> question. I have an equation with 3 unknowns. f= P/ (r+p) pow(B). I have values KSC> of f for different r's. Can i use R to find the P,p,B values which are KSC> constants. The equation is Manderbolts equation. Yes. Did you mean "how"? -- A.J. Rossini Rsrch. Asst. Prof. of Biostatistics U. of Washington Biostatistics rossini at u.washington.edu FHCRC/SCHARP/HIV Vaccine Trials Net rossini at scharp.org -------------- http://software.biostat.washington.edu/ ---------------- FHCRC: M: 206-667-7025 (fax=4812)|Voicemail is pretty sketchy/use Email UW: Th: 206-543-1044 (fax=3286)|Change last 4 digits of phone to FAX (my tuesday/wednesday/friday locations are completely unpredictable.)
Komanduru Sai C <sck2348 at cacs.louisiana.edu> writes:> I am a grad student at the university of Louisiana at Lafayette. I > have a question. I have an equation with 3 unknowns. f= P/ (r+p) > pow(B). I have values of f for different r's. Can i use R to find > the P,p,B values which are constants. The equation is Manderbolts > equation.You may want to use nonlinear least squares to fit the parameters in this model. To do so you will need starting values for the parameters p and B. Suppose that the starting value for p is 0.1 and for B is 2 and that your data are in a data frame called KSC. fm = nls(y ~ 1/((r+p)^B), data = KSC, start = c(p=0.1, B=2), alg='plinear', trace = TRUE) coef(fm) Use of nls assumes that the observations consist of 'signal + noise' and the 'noise' part has constant variance. See, for example, Bates and Watts (1988), "Nonlinear Regression Analysis and Its Applications", Wiley.