[R] substituting string variable in expression with its value

[Jannis]

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
>>
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>