If you want to fit "y = a + bx", then you use "lm(y ~ x)" instead of "lm(y ~ A + bx)". 'A' is not a parameter but coefficient and you do not need to specify coefficients, which is what the linear model is trying to do anyway ! See the details section of help("formula").
> x <- 1:5 > y <- c(0, 1.0, 1.7, 2.0, 2.1) > lm(x ~ y) Call: lm(formula = x ~ y) Coefficients: (Intercept) y 0.6828 1.7038 If A was already defined, and you are trying to multiply the y-values, then use the I() operator. This protects the term/calculation and inhibits the usual term interpretation in linear models. > lm(x ~ I(2*y) ) Call: lm(formula = x ~ I(2 * y)) Coefficients: (Intercept) I(2 * y) 0.6828 0.8519 PS : I think there is a typo in the y input as there is no such number as 2.1.4 On Thu, 2004-07-15 at 16:28, [EMAIL PROTECTED] wrote: > Hi, i 'dont understand how to take a general formula, view this: > > x<-1:5 > y<-c(0,1,1.7,2,2.1.4) > dummy<-data.frame(x=x,y=y) > formula<-"y~A*log(x)/log(2)" > formu<-as.formula(formula) > fm<-lm(formu,data=dummy) > Error in eval(expr, envir, enclos) : Object "A" not found > > but A is the parameter of fitting, why is this?Thanks Ruben > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html