[R] Help with expression()

[Sheri O'Connor]

Thanks very much! bquote() did the trick!

on Thu, Oct 10, 2013 at 6:19 PM, William Dunlap <wdunlap at tibco.com> wrote:
>> changetext = expression(paste("Change from ",mini," to ", maxi, ":",
>> diff ,degree,"C",collapse=""))
>>
>> does not evaluate my user defined variables - mini,maxi, and diff -
>> just printing them out as words
>
> bquote() can do it: put the variables which should be evaluated in .().  E.g.,
>     mini <- 13
>     maxi <- 97
>     diff <- maxi - mini
>     plot(0, 0, main=bquote("Change from" ~ .(mini) ~ "to" ~ .(maxi) * ":" ~ .(diff) ~ degree ~ "C"))
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
>
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
>> Of Sheri O'Connor
>> Sent: Thursday, October 10, 2013 1:08 PM
>> To: R-help at r-project.org
>> Subject: [R] Help with expression()
>>
>> Hi everyone,
>>
>> I am hoping someone can help with my attempted use of the expression
>> function. I have a long series of text and variable to paste together
>> including a degree symbol. The text is to be placed on my scatter plot
>> using the mtext function.
>>
>> Using expression like this:
>>
>> changetext = expression(paste("Change from ",mini," to ", maxi, ":",
>> diff ,degree,"C",collapse=""))
>>
>> does not evaluate my user defined variables - mini,maxi, and diff -
>> just printing them out as words
>>
>> Using expression like this:
>>
>> changetext = paste("Change from ",mini," to ", maxi, ":", diff
>> ,expression(degree,"C"),collapse="")
>>
>> prints the text twice and does not evaluate the degree symbol.
>>
>> I have tried to place the expression alone in a variable and then run the paste:
>>
>> degsym = expression(degree,"C")
>> changetext = paste("Change from ",mini," to ", maxi, ":", diff
>> ,degsym,collapse="")
>>
>> giving me the same result as the second option
>>
>> Is there any way I can use the expression function as in the first
>> example but still have R evaluate my user defined variables?
>>
>> Thanks!
>> Sheri
>>
>> ---
>> Sheri O'Connor
>> M.Sc Candidate
>> Department of Biology
>> Lakehead University  - Thunder Bay/Orillia
>> 500 University Avenue
>> Orillia, ON L3V 0B9
>>
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