Is this what you want? myTitle <- function (name, unitsExpr = parse(text = unitsString)[[1]], unitsString) { name <- as.name(name) bquote(.(name) ~ "[" * .(unitsExpr) * "]") } plot(1,1,xlab=myTitle("velocity", quote(km/hr)), ylab=myTitle("distance", quote(light~years)))
Note that unitsExpr should be an expression (typically as quote(...)) but if you hate expressions you can give a string to unitsString, which will be parsed to form the expression. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of Jannis > Sent: Thursday, September 12, 2013 7:53 AM > To: Gerrit Eichner > Cc: r-help@r-project.org > Subject: Re: [R] substituting string variable in expression with its value > > Hi Gerrit, > > thanks for your suggestion. I want to create some code were I can supply > the 'm*s^{-2}' part as an argument to a function and which evaluates > this as an expression to use Rs mathematical annotation features in the > labels. > > > Any further ideas? > > Jannis > > > > On 12.09.2013 14:28, Gerrit Eichner wrote: > > Hi, Jannis, > > > > maybe > > > > plot( 1, 1, main = bquote( paste( .(a), " [", .(b), "]"))) > > > > > > comes close to what you want, but I think you may even have to use the > > following to get a varying exponent really printed elevated: > > > > a <- "speed" > > b <- "m * s" > > cc <- -2 > > > > plot( 1, 1, main = bquote( paste( .(a), " [", .(b)^{.(cc)}, "]"))) > > > > > > > > Hth -- Gerrit > > > > > >> plot(1,1, main=expression(paste("speed [", m * s^{-1}, "]"))) > >> > >> > >> I would, however, like to be able to supply the value "speed" and > >> m*s^{-a} by variables, e.g. do something like: > >> > >> > >> a = 'speed' > >> b = 'm*s^{-2}' > >> > >> plot(1,1, main=expression(paste(a, " [", b, "]"))) > >> > >> This, however, does not work as a and b are not treated as variable > >> names in this case. Does anyone have a solution for this? > >> > >> > >> Cheers > >> jannis > >> > >> ______________________________________________ > >> 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. > > > > > > ______________________________________________ > 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. ______________________________________________ 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.