R help - Sep 2013 - substituting string variable in expression with its value

Hi,


the following code works:

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

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
>
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