[R] How to concatenate expressions

[Sebastien Bihorel]

Thanks a bunch, Baptiste,

Your lapply call works like a charm. BTW, it works also if a, b, and c 
are expressions :D

Sebastien

baptiste auguie wrote:
> Hi,
>
> You can try this, though I hope to learn of a better way to do it,
>
> a = c(quote(alpha),quote(beta),quote(gamma))
> b = lapply(1:3, function(x) as.character(x))
> c = c(quote('-10'^th),
>   quote('-20'^th),
>   quote('-30'^th))
>
> testplot <- function(a,b,c) {
>
>  text <-
>    lapply(seq_along(a), function(ii) bquote(.(a[[ii]])*.(b[[ii]])*.(c[[ii]])))
>
>  dev.new()
>
>  plot(-5:5,-5:5,col=0)
>
>  for (i in seq_along(a)) {
>    text(x=i,
>        y=i,
>        labels=text[[i]])
>  }
> }
>
> testplot(a,b,c)
>
> HTH,
>
> baptiste
>
> 2009/11/20 Sebastien Bihorel <Sebastien.Bihorel at cognigencorp.com>:
>   
>> Dear R-users,
>>
>> I am developing a plotting function, which receives expressions and
>> character/numerical vectors as part of the many input arguments and which
>> tries to concatenate them before displaying the result to the plot. I
>> currently cannot find a way to make this concatenation works. I have read
>> several posts in the list that solved this problem by pasting the different
>> elements together before creating the expressions (like in
>> http://tolstoy.newcastle.edu.au/R/help/02a/4790.html). I cannot implement
>> this solution because my expressions and numerical/character vectors are
>> passed to the function and not create inside the function. I would greatly
>> appreciate any help with the following example code.
>>
>> Thank you
>>
>>
>> testplot <- function(a,b,c) {
>>
>>  text <- as.expression(paste(a,b,c,sep=' '))
>>
>>  dev.new()
>>
>>  plot(-5:5,-5:5,col=0)
>>
>>  for (i in 1:3) {   text(x=i,
>>        y=i,
>>        labels=text[i])
>>  }
>> }
>>
>> a <- as.expression(c(bquote(alpha),bquote(beta),bquote(gamma)))
>>
>> b <- as.expression(1:3)
>>
>> c <- as.expression(c(bquote('-10'^th),
>>                    bquote('-20'^th),
>>                    bquote('-30'^th)))
>>
>> testplot(a,b,c)
>>
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>> 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.
>>
>>