search for: ssmicmen

Dear list, Has anyone created a version of SSmicmen that allows testing for group differences? The basic Michaelis-Menten equation is: (Bmax * X) / (Kd + X). The nlme package allows modeling of random effects for Bmax and Kd as needed, but I curious how I can build in group differences? I have receptor binding data for strains of mice, and f...

...symptotic the data were). Many thanks, in advance. roly russell - oregon state university PS - I have not consulted Bates & Watts yet; I will. # build artificial data with multiplicative error Dat <- NULL; Dat$x <- rep(seq(1,25,by=3), 5) set.seed(1) Dat$y <- SSmicmen(Dat$x, 50, 12)*rnorm(45, 1, 0.1) plot(Dat) # fit a classical least-square regression Dat.nls <- nls(y ~ SSmicmen(x, Vmax, Km), data=Dat); Dat.nls lines(1:25, predict(Dat.nls, newdata=list(x=1:25)), col=1) # the 1st and 3rd quartiles regressions Dat.nlrq <- nlrq(y...

...13333 3 894.5300 0.6393333 4 782.3800 0.5836667 5 857.5900 0.6003333 6 829.2700 0.5883333 I have fit the data using logistic, Michaelis?Menten, and linear model, they all give significance. > fm1 <- nls(Biomass~SSlogis(P, phi1, phi2, phi3), data=Ca.P.Biomass.A) > fm2 <- nls(Biomass~SSmicmen(P, phi1, phi2), data=Ca.P.Biomass.A) > fm3 <- lm(Biomass~P, data = Ca.P.Biomass.A) I hope to compare the difference among the three models, and I using anova(). As for the example here, the three models seem not have significant difference. However, I am confused by the negative df in the...

Dear all, I am trying to define a selfStart function for a non-linear model, which is a log-transformed SSmicmen model with multiplicative errors and so it is required to make them additive: log(y)=log(a)+log(x)-log(1+x/b) Any ideas about how to use the "peeling" method to derive the "initial" argument and get the initial values? Thank you for being always there!:) Irene

Hello! I work with : R : Copyright 2006, The R Foundation for Statistical Computing Version 2.3.1 (2006-06-01) On Windows XP Professional (Version 2002) SP2. At this moment I use the function "nls" combined with a selfStar model (SSmicmen, related to Michaelis-Menten equation, and provided by the "stats" package). When I realise the following operation (cf. p 59 of the "An Introduction to R" manual, http://www.r-project.org/, for more details): > fit<-nls(y~SSmicmen(x, Vm, K), df) > summary(fit) I ob...

..., p[3], p[4], p[5]. I plotted the x-y data. Then I used lines(spline(xfit,yfit)) to overlay best curves on the data while changing the parameters. My question is how do I calculate the residual sum of squares. In the example they have the following: df <- data.frame( x=x, y=y) fit <- nls(y ~SSmicmen(s, Vm, K), df) fit In the second line how would I input my function? Would it be: fit <- nls(y ~ myfunction(p[1], p[2], p[3], p[4], p[5]), df) where myfunction is the actual function? My function doesnt have a name, so should I just enter it? Thanks -- View this message in context: http:/...

Hello list: How to extract the value of "Rho" from a gnls() object. I am using gnls() function similar to res <- gnls(y~SSmicmen(),correlation=corCompSymm(form~1|b),data=dat) Thanks in advance, Mahbub. -- Mahbub Latif School of Mathematical Sciences Queen Mary, University of London United Kingdom [[alternative HTML version deleted]]

Hi there are some predefined self-start functions, like SSmicmen, SSbiexp, SSasymp, SSasympOff, SSasympOrig, SSgompertz, SSflp, SSlogis, SSweibull, Quadratic, Qubic, SSexp (nlrwr) Btw, do you know graphic examples for this functions? The SSexpDecay (exponential decay) for y = (y0 - plateau)*exp(-k*x) + plateau from http://stats.stackexchange.com/questions/1712...

Dear all, I noticed the following under R 1.8.1 (when nls was still a separate package) but the same problem occurs under R 1.9.0 (where most (all?) of nls is now in the stats package): > data(Puromycin) > fm <- nls(rate~SSmicmen(conc,b0,b1), Puromycin, subset = state=="treated") > coef(summary(fm)) NULL The problem seems to be that summary.nls uses the name "parameters" instead of the name "coefficients" for the matrix with the estimates, standard errors, t values and p values: > summa...

.../R/library/nls/R-ex/SSbiexp.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/SSfol.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/SSfpl.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/SSlogis.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/SSmicmen.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/asOneSidedFormula.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/clearNames.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/formula.nls.R action: create D: file: /usr/local/lib/R/library/nls/R-ex/getIni...

...html latex example SSfol text html latex example SSfpl text html latex example SSgompertz text html latex example SSlogis text html latex example SSmicmen text html latex example SSweibull text html latex example Theoph text html latex example asOneSidedFormula text html latex example clearNames te...