Alternatively, perhaps strsplit() with an appropriate regex argument.
See ?strsplit ?regexp
e.g.
strsplit ("z<=5",split = "[<>=]+")
[[1]]
[1] "z" "5"
This of course will only work if you know what the characters are that
define "left" and "right", how complex the expressions might be, etc.
-- i.e. the simple case.
-- Bert
On Wed, Jul 3, 2013 at 10:55 AM, William Dunlap <wdun...@tibco.com> wrote:
> If your syntax is like R's syntax then parse() can help.
> R> p <- parse(text="z = 1 + 2")
> R> p[[1]] # the first (& only) expression in "z = 1 + 2"
> z = 1 + 2
> R> as.list(p[[1]]) # the 'function' called (`=`) and its 'arguments'
> [[1]]
> `=`
>
> [[2]]
> z
>
> [[3]]
> 1 + 2
>
> R> as.list(p[[1]][[3]]) # ditto for the 2nd argument above
> [[1]]
> `+`
>
> [[2]]
> [1] 1
>
> [[3]]
> [1] 2
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
>
>> -----Original Message-----
>> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
>> Behalf
>> Of Dan Murphy
>> Sent: Wednesday, July 03, 2013 10:38 AM
>> To: R-help@r-project.org
>> Subject: [R] Splitting a string expression into components
>>
>> I have a vector of strings that contain mathematical expressions. E.g.,
>> x <- c("5 <= 7", "z = 1+2")
>> and I would like to decompose each expression into its left- and
>> right-hand-side components etc., output something like
>>
>> "5" "<=" "7"
>> "z" "=" "1" "+" "2"
>>
>> Is there something built into the R language to accomplish this?
>> Thanks for advance.
>> Dan
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> 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.
>
> ______________________________________________
> R-help@r-project.org mailing list
> 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.
--
Bert Gunter
Genentech Nonclinical Biostatistics
Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
