Hi Emily, Yes (see below), but you might be better off by writing a simple function. Here are examples both ways (usually eval parse is highly discouraged).
Cheers, Josh ######################### eqn1string <- "x^2 + x + 5" x <- 6 ## works eval(parse(text = eqn1string)) ## better f <- function(x) { x^2 + x + 5 } f(6) ## this is more flexible f(c(6, 5, 3, 10, 20)) ## plot function curve(f, from = -20, to = 20) ## find minimum in a range optimize(f = f, interval = c(-300, 300)) ## minimum is the value of x that yields the smallest value of ## the objective function, i.e. f(-.5) ######################### On Wed, Mar 14, 2012 at 11:39 PM, Emily Weiser <emily.l.wei...@gmail.com> wrote: > I'm trying to figure out if it's possible to use a character string as an > equation, e.g: > > eqn1string <- "x^2 + x + 5" > > Then I want to tell R: > 1) that eqn1string is actually an equation (even though it was stored as a > character string), and > 2) to apply the equation to a specified value of x (e.g. given x <- 6, > what is the result of the equation). > > Thanks in advance for any insight anyone may be able to offer. > > Emily > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. -- Joshua Wiley Ph.D. Student, Health Psychology Programmer Analyst II, Statistical Consulting Group University of California, Los Angeles https://joshuawiley.com/ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.