Hi: On Fri, Jun 25, 2010 at 6:12 PM, Vadim Ogranovich < vogranov...@jumptrading.com> wrote:
> Dear R users, > > Please disregard my previous post "converting result of substitute to > 'ordidnary' expression". The problem I have has nothing to do with > substitute. > > Consider: > > > dat <- data.frame(x=1:10, y=1:10) > > > subsetexp <- expression(5<x) > > class(subsetexp) [1] "expression" > > ## this does work > > subset(dat, eval(subsetexp)) > x y > 6 6 6 > 7 7 7 > 8 8 8 > 9 9 9 > 10 10 10 > > eval(subsetexp) [1] FALSE FALSE FALSE FALSE FALSE TRUE TRUE TRUE TRUE TRUE > > > > ## and so does this > > subset(dat, 5<x) > x y > 6 6 6 > 7 7 7 > 8 8 8 > 9 9 9 > 10 10 10 > > 5 < x [1] FALSE FALSE FALSE FALSE FALSE TRUE TRUE TRUE TRUE TRUE > > > ## but this doesn't work > > subset(dat, subsetexp) > Error in subset.data.frame(dat, subsetexp) : > 'subset' must evaluate to logical > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Why did the last expression fail and why it worked with eval()? > subsetexp is an object of class expression, whereas the second argument of subset() expects a logical [vector]. As shown above, both 5 < x and eval(subsetexp) evaluate to logical vectors. HTH, Dennis > > Thank you very much for your help, > Vadim > > Note: This email is for the confidential use of the named addressee(s) only > and may contain proprietary, confidential or privileged information. If you > are not the intended recipient, you are hereby notified that any review, > dissemination or copying of this email is strictly prohibited, and to please > notify the sender immediately and destroy this email and any attachments. > Email transmission cannot be guaranteed to be secure or error-free. Jump > Trading, therefore, does not make any guarantees as to the completeness or > accuracy of this email or any attachments. This email is for informational > purposes only and does not constitute a recommendation, offer, request or > solicitation of any kind to buy, sell, subscribe, redeem or perform any type > of transaction of a financial product. > > ______________________________________________ > 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. > [[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.
