need suggestion about building formual

Thanks for your kind respond. Although the answer didn't solve my question 
clearly,maybe I still not understand the art of R.

I'm sorry that I had not talked the problem clearly, maybe a example with more 
detail will be suitable as suggested in the the posting guide.
 
In function fitting program, such as Sigmaplot, a fitting formula, can be  
write in separate form:
G=a+(b*x)^(1/2)
k=exp((G-G0)/(R*T))
fit k to y

of course,in R's nls, can write as:
mynls<-nls(formula=y~exp((a+(b*x)^(1/2)-G0)/(R*T)),data=mydata,...)

In this example, the formula is simple and acceptable. However, when the 
formula is more complexity,writing all in one formula,the readability will be 
damaged.So I'm looking for a way to write simple and readable code in this 
situation.   

  
Spencer Graves wrote:

  I'm not certain what you are asking.

  You can build expressions in R as character strings and then execute
them.  Example:

expr <- paste("two <-", 1, "+", 1)
eval(parse(text=expr))
two

  If this does not answer your question, PLEASE do read the posting
guide, "www.R-project.org/posting-guide.html".  It can help increase the
chances of a quick and useful reply.

  spencer graves

Simple wrote:

hi,
I'm an newbie for R,I want do some fitting in R.

I wander if it is possible to write a few of equations but only one
formual when fitting

Currently,My problem is,in R, is there methods combination a few
equations into one formual?
For example,
y=f1(k);
k=f2(t);
t=f3(x);
although it is certain that the can be equations turn into one formual as
y~f(x),but write such a complexity string make me painful.

I have searched the web and found out there were only examples with one
formual.any suggestion?

I hope that I have omit something.

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