[R] combining grid.text, expression and variables

[Sebastien Bihorel]

Hi Baptiste,

Thank for the help. One thing though that I found while transposing your 
syntax to my problem: lab must be of class expression for your syntax to 
work. For instance, if one replaces the second elements of the lab 
variables by a simple integer, lab is not more of class expression, and 
grid.text just displays strings of character.

An easy way to bullet proof the code: use as.expression when building lab

Thanks

baptiste auguie wrote:
> Hi,
>
> Try this,
>
>
> library(grid)
>
> value <- c(0.1)
>
> lab <- c("test",
>          expression(bquote(paste(.(value[1]*100), " and percentiles1", 
> sep=""))),
>          bquote(expression(.(value[1]*100)*" and percentiles2")),
>          bquote(paste(.(value[1]*100), " and percentiles3", sep="")) )
>
>
> grid.newpage()
>  grid.text(eval(lab[1]), x=0.5, y=unit(1,"npc")-unit(1,"lines"))
>  grid.text(eval(lab[2]), x=0.5, y=unit(1,"npc")-unit(2,"lines"))
>  grid.text(eval(lab[3]), x=0.5, y=unit(1,"npc")-unit(3,"lines"))
>  grid.text(lab[4], x=0.5, y=unit(1,"npc")-unit(4,"lines"))
>
> My preference goes for the last one.
>
> HTH,
>
> baptiste
>
> 2009/9/2 Sebastien Bihorel <sebastien.bihorel at cognigencorp.com 
> <mailto:sebastien.bihorel at cognigencorp.com>>
>
>     Dear R-users,
>
>     I am trying to use the grid.text and expression functions to
>     display several character strings and plotmath text on a viewport.
>     Some strings can include a variable portion (PI.limits in the
>     following example), which I thought could be implemented by
>     combining the bquote and the expression functions. Unfortunately,
>     my expressions do not seem to be evaluated. I would greatly
>     appreciate if somebody could tell me where my mistake(s) is(are).
>
>     Thank you in advance
>
>
>     ###### 8< #######
>
>     library(grid)
>
>     PI.limits <- c(0.1,0.9)
>
>     vp.ref <- c("raw data","median","median",
>                    bquote(expression(paste(.(PI.limits[1]*100), " and ",
>                                            .(PI.limits[2]*100)^th,"
>     percentiles", sep=""))),
>                    bquote(expression(paste(95^th,"confidence interval
>     on percentiles", sep=" "))),
>                    bquote(expression(paste(95^th,"confidence interval
>     on percentiles", sep=" ")))
>                    )
>
>
>     grid.newpage()
>
>     for (i in c(1,3,4,5,6)) {
>      grid.text(eval(vp.ref[i]), x=0.5, y=unit(1,"npc")-unit(i,"lines"))
>     }
>
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>     PLEASE do read the posting guide
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>     and provide commented, minimal, self-contained, reproducible code.
>
>
>
>
> -- 
> _____________________________
>
> Baptiste Auguié
>
> School of Physics
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
>
> http://newton.ex.ac.uk/research/emag
> ______________________________
>