Message-ID: <22351.54958.798111.429036@stat.math.ethz.ch>
Date: 2016-06-02T06:48:14Z
From: Martin Maechler
Subject: Making an if condition variable ?
In-Reply-To: <CA+8X3fVFKqQ+KX9PtCLQB3QK=+Ti0WzE8p9AKDw4A0BDo-Yw6A@mail.gmail.com>
>>>>> Jim Lemon <drjimlemon at gmail.com>
>>>>> on Thu, 2 Jun 2016 13:03:01 +1000 writes:
> Hi ce,
> a<-10
> condition<-expression("a>0")
> if(eval(parse(text=condition))) cat("a>0\n")
While this may answer the question asked,
the above is *not* good advice, excuse me, Jim :
> fortune(106)
If the answer is parse() you should usually rethink the question.
-- Thomas Lumley
R-help (February 2005)
> fortune(181)
Personally I have never regretted trying not to underestimate my own future stupidity.
-- Greg Snow (explaining why eval(parse(...)) is often suboptimal, answering a question
triggered by the infamous fortune(106))
R-help (January 2007)
---------------------
Good advice would emphasize to use expressions rather than
strings.... and yes that's a bit more sophistication.
But it's worth it.
Martin
>
> Jim
> On Thu, Jun 2, 2016 at 12:30 PM, ce <zadig_1 at excite.com> wrote:
>>
>> Dear all,
>>
>> I want to make an if condition variable like :
>>
>> a = 10
>> CONDITION = " a > 0 "
>>
>> if ( CONDITION ) print(" a is bigger" )
>>
>> I tried get , getElement , eval without success ?
>>
>> Thanks
>>
>> ______________________________________________
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> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.